View source for M4 carbine

{{Short description|American assault rifle}}
{{Redirect2|M4A1|Colt M4||M4 (disambiguation)}}
{{Redirect-distinguish|M16 carbine|CAR-15}}
{{Use dmy dates|date=June 2022}}
{{Infobox weapon
| name               = Carbine, Caliber 5.56 mm, M4
| image              = File:PEO M4 Carbine RAS M68 CCO.png
| image_size         = 300
| caption            = Colt M4 carbine with [[#M4 MWS (Modular Weapon System)|RAS]], [[M68 CCO]]
| origin             = [[United States]]
| type               = {{ubli
  | [[Assault rifle]]
  | [[Carbine]]
}}
| is_ranged          = yes
<!-- Service history -->
| service            = 1994–present
| used_by            = See ''[[#Users|Users]]''
| wars               = See ''[[#Conflicts|Conflicts]]''
<!-- Production history -->
| designer           = 
| design_date        = 1982–1993
| manufacturer       = {{ubl
  | [[Colt's Manufacturing Company]]
  | [[FN Herstal]]
  | [[Remington Arms]]
}}
| unit_cost          = $700 (avg. cost) in 2012<ref name="militarytimes1">{{cite web |last=Curtis |first=Rob |url=http://militarytimes.com/blogs/gearscout/2012/04/20/us-army-places-order-for-24000-m4-carbines-with-remington/ |title=U.S. Army places order for 24,000 M4A1 carbines with Remington |publisher=Military Times |date=2012-04-20 |access-date=2012-08-23 |archive-url=https://web.archive.org/web/20120624094006/http://militarytimes.com/blogs/gearscout/2012/04/20/us-army-places-order-for-24000-m4-carbines-with-remington/ |archive-date=2012-06-24 |url-status=live}}</ref> <br /> $647 per unit in 2015
| production_date    = 1987–present{{Sfn|Rottman|2011|p=36}}
| number             = 500,000 (as of 2021){{Sfn|McNab|2021|p=57}}
| variants           = See ''[[#Variants|Variants]]''
<!-- General specifications -->
| spec_label         = 
| weight             = {{ubli|{{convert|6.43|lb|kg|abbr=on}} empty{{Sfn|McNab|2021|p=13}} |{{convert|7.75|lb|kg|abbr=on}} with 30 rounds loaded magazine and [[Sling (firearms)|sling]]}}
| length             = {{ubli|{{convert|33|in|mm|0|abbr=on}} ([[Stock (firearms)|stock]] extended) |{{convert|29.75|in|mm|abbr=on}} (stock retracted)}}
| part_length        = {{convert|14.5|in|mm|0|abbr=on}}
| width              = 
| height             = 
| diameter           = 
| crew               = <!-- Ranged weapon specifications -->
| cartridge          = [[5.56×45mm NATO]]
| cartridge_weight   = 
| action             = [[Gas-operated]], [[Closed bolt|closed]] [[rotating bolt]], [[Direct impingement#Stoner bolt and carrier piston system|Stoner bolt and carrier piston]]
| rate               = 700–970 rounds/min cyclic<ref name="Army_fact_file"/>
| velocity           = {{ubli
  | {{convert|2970|ft/s|m/s|abbr=on}} ([[5.56×45mm NATO#M855A1|M855A1]] round)<ref>{{cite web|url=https://acc.dau.mil/adl/en-US/382846/file/68848/Public%20Release%20EPR%20Apr12.pdf|title=M855A1 Enhanced Performance Round (EPR), LTC Philip Clark, Product Manager Small Caliber Ammunition, April 2012|access-date=2017-02-25|archive-url=https://web.archive.org/web/20170125120308/https://acc.dau.mil/adl/en-US/382846/file/68848/Public%20Release%20EPR%20Apr12.pdf|archive-date=2017-01-25|url-status=dead}}</ref>
  | {{convert|2887|ft/s|m/s|abbr=on}} (M855 round) |{{convert|2986|ft/s|m/s|abbr=on}} (M193 round)
}}
| range              = {{ubli
  | {{convert|500|m|yd|abbr=on}} (individual/point targets)<ref name="Army_fact_file"/>
  | {{convert|600|m|yd|abbr=on}} (area targets)<ref name="Army_fact_file"/>
}}
| max_range          = {{convert|3600|m|yd|abbr=on}}<ref name="Army_fact_file"/>
| feed               = 30-round detachable [[STANAG magazine]]{{efn|Magazines with different capacities also available}}
| sights             = [[Iron sights]] or various optics
}}

The '''M4 carbine''' (officially '''Carbine, Caliber 5.56&nbsp;mm, M4''') is an [[assault rifle]] developed in the United States during the 1980s. It is a shortened version of the [[M16A2 rifle|M16A2]] assault rifle. The M4 is extensively used by the [[United States Armed Forces|US military]], with decisions to largely replace the M16 rifle in [[United States Army|US Army]] (starting 2010) and [[United States Marine Corps|US Marine Corps]] (starting 2016) combat units as the primary [[infantry]] weapon<ref name="Small Arms–Individual Weapons">{{cite web |title=Small Arms–Individual Weapons |url=https://fas.org/man/dod-101/sys/land/wsh2011/290.pdf |website=Federation of American Scientists (FAS) |date=3 November 2010 |access-date=8 November 2010 |archive-url=https://web.archive.org/web/20110209114148/http://www.fas.org/man/dod-101/sys/land/wsh2011/290.pdf |archive-date=9 February 2011 |url-status=live}}</ref><ref name="Commandant approves M4 as standard weapon for Marine infantry">{{cite web |title=Marine grunts react to switch from the M16 to the M4 |website=Marine Corps Times |date=November 1, 2015 |url=https://www.marinecorpstimes.com/news/your-marine-corps/2015/11/01/marine-grunts-react-to-switch-from-the-m16-to-the-m4/ |access-date=2023-02-04 |archive-url=https://web.archive.org/web/20160425045929/http://www.marinecorpstimes.com/story/military/tech/2015/11/01/marine-grunts-react-switch-m16-m4/74849998/ |archive-date=2016-04-25 |url-status=live}}</ref> and [[service rifle]]. The M4 has been adopted by over 60 countries worldwide,{{Sfn|McNab|2021|p=5}} and has been described as "one of the defining firearms of the 21st century".{{Sfn|McNab|2021|p=6}}

Since its adoption in 1994,{{Sfn|McNab|2021|p=5}} the M4 has undergone over 90 modifications to improve the weapon's [[adaptability]], [[ergonomics]] and [[modularity]], including: the M4A1, which possesses a thicker barrel and a replacement of the [[Burst mode (weapons)|burst-fire]] control group with a fully [[automatic firearm|automatic]] one; the [[SOPMOD]], an accessory kit containing optical attachments; and the underbarrel weapons such as [[M203 grenade launcher|M203]] and [[M320 Grenade Launcher Module|M320]] [[grenade launcher]]s to the [[Knight's Armament Company Masterkey|Masterkey]] and [[M26 Modular Accessory Shotgun System|M26-MASS]] [[shotgun]]s.

In April 2022, the U.S. Army selected the [[M7 rifle]], a variant of the [[SIG MCX Spear]], as the winner of the [[Next Generation Squad Weapon Program]] to replace the M16/M4.<ref>{{cite web |url=https://www.armytimes.com/news/your-army/2022/04/19/army-chooses-sig-sauer-to-build-its-next-generation-squad-weapon/ |title=Army chooses Sig Sauer to build its Next Generation Squad Weapon |website=Army Times |date=19 April 2022}}</ref>

==History==

=== Development of the M4 ===
Following the military adoption of the [[Armalite AR-15]] as the [[M16 rifle]], [[carbine]] variants were also adopted for [[Close-quarters combat|CQC]] operations,{{Sfn|McNab|2021|p=7}} the first of which was the [[CAR-15]] family of weapons, which was used in the [[Vietnam War]].{{Sfn|McNab|2021|p=8}} However, these rifles had design issues, as the [[Gun barrel|barrel]] length was halved to {{convert|10|in|cm}}, which upset the [[ballistics]], reducing its range and accuracy and leading to considerable [[muzzle flash]] and blast,{{Sfn|McNab|2021|p=9}} meaning that a large [[flash suppressor]] had to be fitted.{{Sfn|Hogg|Weeks|2000|p=166}}

In 1982, the U.S. Government requested [[Colt's Manufacturing Company|Colt]] to make a carbine version of the M16A2. At the time, the Colt M16A2 was the Colt 645, also known as the M16A1E1. Later that year, the U.S. Army Armament Munitions Chemical Command helped Colt develop a new variant of the XM177E2, and the U.S. Army redesignated the XM177E2 to the XM4 Carbine, giving the name as the successor to the [[M1 carbine|M3 carbine]]. The carbine used the same upper and lower [[Receiver (firearms)|receiver]] as the M16A1,{{Sfn|McNab|2021|p=10}} and fires the M855 cartridge along with the older M193 cartridges. In 1983, the [[9th Infantry Division (United States)|9th Infantry Division]] requested a Quick Reaction Program (QRP) for a [[5.56mm]] carbine to replace the M1 carbine and [[M3 submachine gun]] in service.{{Sfn|Rottman|2011|p=43}}{{Sfn|McNab|2021|p=9}} The XM4 was tested by the Army's Armament Research and Development Center (ARDC) in June 1983. Later, the gun was updated with improved furniture, and a barrel with rifling of 1 turn in {{convert|7|in}}. The ARDC recommended additional commonality with the M16A2 rifle, as well as lengthening the barrel to {{convert|14.5|in}}.{{Sfn|McNab|2021|p=10}} In January 1984, the U.S. Army revised the QRP, and a month later, it formally approved development of the new carbine.{{Sfn|McNab|2021|p=10}}

In June 1985, the [[Picatinny Arsenal]] was given a contract to produce 40 prototypes of the XM4.{{Sfn|McNab|2021|p=10}} Initially a joint program between the Army and Marines, in 1986 the Army withdrew their funding. The XM4 was finished in 1987, and the Marines adopted 892 for that [[fiscal year]], with the designation "carbine, 5.56mm, M4".{{Sfn|McNab|2021|p=10}} Owing to experience from the 1991 [[Gulf War]], the Army gave Colt its first production contracts for M4 carbines in May and July 1993, and M4A1 carbines for [[United States Special Operations Command]] (SOCOM) operators in February 1994.{{Sfn|McNab|2021|p=14}}

Interest in the M4 carbine was accelerated after the [[Battle of Mogadishu (1993)]], in which [[United States Army Rangers|Rangers]] complained that their M16 rifles were "unwieldy", whereas members of [[Delta Force]] in the same battle, equipped with the CAR-15, had no such complaints.{{Sfn|McNab|2021|p=46}} The M4 carbine first saw action in the hands of U.S. troops deployed to [[Kosovo]] in 1999 in support of the [[NATO]]-led [[Kosovo Force]].{{Sfn|McNab|2021|p=47}} It would subsequently be used heavily by U.S. forces during the [[war on terror]], including in [[Operation Enduring Freedom]] and the [[Iraq War]].{{Sfn|McNab|2021|p=47}} In the Army, the M4 had largely replaced M16A2s as the primary weapon of forward deployed personnel by 2005.<ref name="Design_SOC" /> The M4 carbine also replaced most submachine guns and selected handguns in U.S. military service,<ref name="Design_SOC" /> as it fires more effective rifle ammunition that offers superior [[stopping power]] and is better able to penetrate modern [[body armor]].{{Sfn|McNab|2021|p=47}}

{{multiple image
| align             = right
| direction         = vertical
| width             = 217
| image1            = DOUBLE EAGLE '95 DF-ST-98-01429.jpg
| caption1          = A [[10th Special Forces Group (United States)|10th Special Forces Group]] soldier with an M4 carbine during an exercise in July 1995
| image2            = Defense.gov News Photo 000109-A-4385T-009.jpg
| caption2          = A U.S. Army [[82nd Airborne]] soldier holds an M4 carbine in [[Vitina]], [[Kosovo]] in January 2000 during the NATO-led [[Kosovo Force|KFOR]] mission, the first operational use of the M4 by U.S. troops
}}
In 2007, the USMC ordered its [[Officer (armed forces)|officers]] (up to the [[Military rank|rank]] of [[Lieutenant colonel (United States)|lieutenant colonel]]) and [[Military staff|staff]] [[non-commissioned officer]]s to carry the M4 carbine instead of the [[Beretta M9|M9]] handgun.<ref>{{cite web |url=http://www.marinecorpstimes.com/article/20070625/NEWS/706250319/Officers-staff-NCOs-issued-M4s |title= Officers, staff NCOs to be issued M4s |publisher= Marine Corps Times |date= 25 June 2007 |url-status=dead |via=Leatherneck.com forums |archive-url=https://web.archive.org/web/20141218034001/http://www.marinecorpstimes.com/article/20070625/NEWS/706250319/Officers-staff-NCOs-issued-M4s |archive-date=18 December 2014}} [http://www.leatherneck.com/forums/showthread.php?48982-Officers,%20staff%20NCOs%20to%20be%20issued%20M4s Alt URL]</ref> This is in keeping with the Marine Corps doctrine, "Every Marine a [[rifleman]]."<ref>{{Cite web| title=Today's Rifleman | url=https://apps.dtic.mil/sti/tr/pdf/ADA500034.pdf | archive-url=https://web.archive.org/web/20241213220829/https://apps.dtic.mil/sti/tr/pdf/ADA500034.pdf | archive-date=2024-12-13}}</ref> The Marine Corps, however, chose the full-sized M16A4 over the M4 as its standard infantry rifle. [[United States Navy]] corpsmen E5 and below are also issued M4s instead of the M9.<ref>{{cite news |url=http://www2.marines.mil/news/messages/Pages/2007/Messagesfinal4.aspx |title=New Assignment Rationale for Individual Weapons |work=U.S. Marine Corps |date=22 June 2007 |archive-url=https://web.archive.org/web/20141129181536/http://www2.marines.mil/news/messages/Pages/2007/Messagesfinal4.aspx |archive-date=29 November 2014}}</ref> While ordinary riflemen in the Marine Corps were armed with M16A4s, M4s were fielded by troops in positions where a full-length rifle would be too bulky, including vehicle operators, [[fireteam]] and squad leaders. As of 2013, the U.S. Marine Corps had 80,000 M4 carbines in their inventory.<ref>{{cite web |url=http://www.thefirearmblog.com/blog/2013/04/20/m27-impressions/ |title=M27 First Impressions|archive-url=https://web.archive.org/web/20130508132938/http://www.thefirearmblog.com/blog/2013/04/20/m27-impressions/ |archive-date=8 May 2013 |website=TheFirearmBlog.com |date=20 April 2013}}</ref><ref>{{cite news |url=http://www.militarytimes.com/article/20130429/NEWS04/304260036/Corps-exploring-rifle-upgrades |title=Corps exploring rifle upgrades |archive-url=https://web.archive.org/web/20130501125725/http://www.militarytimes.com/article/20130429/NEWS04/304260036/Corps-exploring-rifle-upgrades |archive-date=1 May 2013 |work=Military Times|date=29 April 2013}}</ref>

By July 2015, major Marine Corps commands were endorsing switching to the M4 over the M16A4 as the standard infantry rifle, just as the Army had done. This is because of the carbine's lighter weight, compact length, and ability to address modern combat situations that happen mostly within close quarters; if a [[squad]] needs to engage at longer ranges, the [[M27 Infantry Automatic Rifle]] can be used as a [[designated marksman rifle]]. Approval of the change would move the M16 to support personnel, while armories already had the 17,000 M4s in the inventory needed to outfit all infantrymen who needed one.<ref>{{cite news |url=http://www.militarytimes.com/story/military/2015/07/27/marine-officials-endorse-infantry-plan--ditch-m16--m4/30145257/ |title=Marine brass endorses infantry plan to ditch M16 for M4 |archive-url=https://web.archive.org/web/20150730224707/http://www.militarytimes.com/story/military/2015/07/27/marine-officials-endorse-infantry-plan--ditch-m16--m4/30145257/ |archive-date=30 July 2015 |work=Military Times |date=27 July 2015}}</ref> In October 2015, [[Commandant of the United States Marine Corps|Commandant]] [[Robert Neller]] formally approved of making the M4 carbine the primary weapon for all infantry battalions, security forces, and supporting schools in the USMC. The switch was to be completed by September 2016.<ref name=":0">{{cite news |url= http://www.militarytimes.com/story/military/2015/10/26/commandant-approves-m4-standard-rifle-marine-corps-infantry/74593750/ |title= Commandant approves M4 as standard weapon for Marine infantry |archive-url=https://web.archive.org/web/20151027200534/http://www.militarytimes.com/story/military/2015/10/26/commandant-approves-m4-standard-rifle-marine-corps-infantry/74593750/ |archive-date=27 October 2015|work=Military Times |date=26 October 2015}}</ref> In December 2017, the Marine Corps revealed a decision to equip every Marine in an infantry squad with the M27, while the M4 would be retained for leadership billets at the platoon level and above.<ref name="kitup5jan18">{{cite news |url=https://www.military.com/kitup/2018/01/05/m27s-and-head-toe-gear-overhaul-way-marine-grunts.html|title=M27s and 'Head-to-Toe' Gear Overhaul on the Way for Marine Grunts |archive-url=https://web.archive.org/web/20180107233105/https://www.military.com/kitup/2018/01/05/m27s-and-head-toe-gear-overhaul-way-marine-grunts.html |archive-date=7 January 2018 |work=Military.com |date=5 January 2018}}</ref> [[United States Marine Forces Special Operations Command|MARSOC]] also retains the M4, as its shorter barrel is more suited to how they operate in confined spaces.<ref>{{cite news |url=https://www.marinecorpstimes.com/news/your-marine-corps/2018/02/23/marine-raiders-dont-want-any-m27s/ |title=Marine Raiders don't want any M27s |archive-url=https://web.archive.org/web/20180224022630/https://www.marinecorpstimes.com/news/your-marine-corps/2018/02/23/marine-raiders-dont-want-any-m27s/ |archive-date=24 February 2018 |work=Marine Corps Times|date=19 February 2018}}</ref>

===Improved M4===
In 2009, the U.S. Army took complete ownership of the M4 design.<ref name="Army acquires rights to M4">{{cite web |url= http://www.armytimes.com/news/2009/07/army_carbine_070609w/ |title=Army acquires rights to M4 |work=[[Army Times]] |access-date=2009-08-18 |date=2009-07-07 |author=Cox, Matthew}}</ref> This allowed companies other than Colt to compete with their own M4 designs. The Army planned on fielding the last of its M4 requirement in 2010.<ref name="Army acquires rights to M4"/> In October 2009, Army weapons officials proposed a series of changes to the M4 to Congress. Requested changes included an electronic round counter that records the number of shots fired, a heavier "SOCOM barrel", and possibly replacing the Stoner expanding gas system with a [[short-stroke piston|gas piston]] system.<ref>[https://patents.google.com/patent/US2951424A/en Stoner expanding gas patient]</ref><ref name="Major revamp possible for M4 carbine">{{cite web |url=http://www.armytimes.com/news/2009/11/army_M4_112109w/ |title=Major revamp possible for M4 carbine |work=[[Army Times]] |access-date=2009-11-21 |date=2009-11-21 |author=Cox, Matthew |archive-url=https://archive.today/20120718070719/http://www.armytimes.com/news/2009/11/army_M4_112109w/ |archive-date=2012-07-18 |url-status=live}}</ref> The heavier "SOCOM barrel" was first issued to special forces operators in the early 2000s to enable greater sustained automatic fire in certain immediate-action drills, although SOCOM itself would eventually return to the standard "government profile" barrel in its subsequent M4 improvement programs.<ref name="URGI_barrel_contract"/>

The benefits of these changes, however, have come under scrutiny from both the military and civilian firearms community.<ref name="Direct Impingement Myth">{{cite web |url=http://www.defensereview.com/the-big-m4-myth-fouling-caused-by-the-direct-impingement-gas-system-makes-the-m4-unreliable/ |title=The Big M4 Myth: "Fouling caused by the direct impingement gas system makes the M4/M4A1 Carbine unreliable." |work=Defensive Review |access-date=2011-07-27 |date=2010-03-19 |author=Pannone, Mike|archive-url=https://web.archive.org/web/20110814165845/http://www.defensereview.com/the-big-m4-myth-fouling-caused-by-the-direct-impingement-gas-system-makes-the-m4-unreliable/ |archive-date=2011-08-14 |url-status=live}}</ref> According to a PDF detailing the M4 Carbine improvement plans released by PEO Soldier, the direct impingement system would be replaced only after reviews were done comparing the direct impingement system to commercial gas piston operating system to find out and use the best available operating system in the U.S. Army's improved M4A1.<ref name="Dual Path Strategy: M4 PIP">{{cite web |title=Dual Path Strategy: M4 PIP |url=https://peosoldier.army.mil/FactSheets/PMSW/Dual_Path_Strategy_M4_PIP.pdf |access-date=7 September 2011|date=7 September 2011}}{{dead link|date=April 2025|bot=medic}}{{cbignore|bot=medic}} </ref>

In September 2010, the Army announced it would buy 12,000 M4A1s from Colt Firearms by the end of 2010, and would order 25,000 more M4A1s by early 2011. Additionally, the service branch planned to buy 12,000 M4A1 conversion kits in early 2011 and bought 65,000 more later that year. Eventually, the Army would upgrade all of its M4s to M4A1s, although the Marine Corps would largely abstain from the effort.<ref name="Army upgrades to M4">{{cite web |title=Corps to pass on Army upgrades to M4 |url=http://marinecorpstimes.com/news/2010/09/marine-corps-passes-on-army-carbine-updates-091110w/ |work=Marine Corps Times |access-date=13 September 2010 |author=Lamothe, Dan|url-status=dead |archive-url=https://web.archive.org/web/20100925141339/http://www.marinecorpstimes.com/news/2010/09/marine-corps-passes-on-army-carbine-updates-091110w/ |archive-date=25 September 2010}}</ref> Conversion of M4s to the M4A1 in the Army began in 2011, as part of the Product Improvement Program, which included the conversion of 300,000 M4 carbines to the M4A1.{{Sfn|McNab|2021|p=16}} The [[101st Airborne Division]] began fielding newly built M4A1s in 2012, and the [[1st Infantry Division (United States)|U.S. 1st Infantry Division]] became the first unit to convert their M4s to M4A1-standard in May 2014. Upgrades included the heavier SOCOM barrel to better dissipate heat from sustained automatic firing, the full-auto trigger group with a more consistent trigger pull than the burst group's to enable better semi-automatic accuracy, and the ambidextrous selector lever for easier use with left-handed shooters. The M4-M4A1 conversion increases weapon weight from {{convert|7.46|lb|kg|abbr=on}} to {{convert|7.74|lb|kg|abbr=on}}, counting a back-up iron sight, forward pistol grip, empty magazine, and sling. Each carbine upgrade costs $240 per rifle, for a total cost of $120&nbsp;million for half a million conversions. Three hundred conversions can be done per day to equip a brigade combat team per week, with all M4A1 conversions to be completed by 2019.<ref>{{cite web |url=https://www.army.mil/article/126553/Beefier_carbines_en_route_to_Soldiers/ |title= Beefier carbines en route to Soldiers|archive-url=https://web.archive.org/web/20140903121037/http://www.army.mil/article/126553/Beefier_carbines_en_route_to_Soldiers/ |archive-date=3 September 2014|website=U.S. Army|url-status=live |date=22 May 2014}}</ref><ref>{{cite web |url=http://www.guns.com/2014/05/24/army-infantry-beginning-adoption-of-upgraded-m4a1-carbines/|title=Army infantry beginning adoption of upgraded M4A1 carbines |archive-url=https://web.archive.org/web/20140903090617/http://www.guns.com/2014/05/24/army-infantry-beginning-adoption-of-upgraded-m4a1-carbines/ |archive-date=3 September 2014 |website=Guns.com |date=24 May 2014}}</ref>

In addition to upgrade kits, in April 2012, the U.S. Army announced it would begin purchasing over 120,000 M4A1 carbines to start reequipping front line units from the original M4 to the new M4A1 version. The first 24,000 were to be made by [[Remington Arms|Remington Arms Company]]. Remington was to produce the M4A1s from mid-2013 to mid-2014.<ref>{{cite web|url=http://militarytimes.com/blogs/gearscout/2012/04/20/us-army-places-order-for-24000-m4-carbines-with-remington/|title=US Army Places Order For 24000 M4 Carbines With Remington|website=Military Times|access-date=24 April 2012|archive-url=https://web.archive.org/web/20120624094006/http://militarytimes.com/blogs/gearscout/2012/04/20/us-army-places-order-for-24000-m4-carbines-with-remington/|archive-date=24 June 2012|url-status=dead}}</ref> After completion of that contract, it was to be between Colt and Remington to produce over 100,000 more M4A1s for the U.S. Army. Because of efforts from Colt to sue the Army to force them not to use Remington to produce M4s, the Army reworked the original solicitation for new M4A1s to avoid legal issues from Colt.<ref>{{cite news |url=http://www.military.com/daily-news/2012/10/18/colt-again-blocks-armys-advanced-m4-plans.html |title=Colt again blocks Army's advanced M4 plans|archive-url=https://web.archive.org/web/20130927144420/http://www.military.com/daily-news/2012/10/18/colt-again-blocks-armys-advanced-m4-plans.html?ESRC=sm_todayinmil.nl |archive-date=27 September 2013 |work=Military.com |date=18 October 2012}}</ref> On 16 November 2012, Colt's protest of Remington receiving the M4A1 production contract was dismissed.<ref>{{cite news |url=http://militarytimes.com/blogs/gearscout/2012/11/28/gao-denies-latest-colt-m4-protest-could-this-be-it/|title=GAO denies latest Colt M4 protest|archive-url=https://web.archive.org/web/20121201142257/http://militarytimes.com/blogs/gearscout/2012/11/28/gao-denies-latest-colt-m4-protest-could-this-be-it/ |archive-date=1 December 2012 |work=Gearscout.com |publisher=Military Times |date=28 November 2012}}</ref> Instead of the contract being re-awarded to Remington, the Army awarded the contract for 120,000 M4A1 carbines worth $77&nbsp;million to [[FN Herstal]] on 22 February 2013.<ref>{{cite news |url=http://kitup.military.com/2013/02/army-awards-m4m4a1-contract-fn.html#more-23457 |title=Army Awards New M4/M4A1 Contract to FN |archive-url=https://web.archive.org/web/20130226042014/http://kitup.military.com/2013/02/army-awards-m4m4a1-contract-fn.html#more-23457 |archive-date=26 February 2013 |work=Military.com |date=23 February 2013}}</ref><ref>{{cite web |url=http://www.thefirearmblog.com/blog/2013/02/24/fn-manufacturing-wins-contract-to-supply-m4a1/ |title=FN Manufacturing Wins Contract to Supply M4A1 |archive-url=https://web.archive.org/web/20130228131919/http://www.thefirearmblog.com/blog/2013/02/24/fn-manufacturing-wins-contract-to-supply-m4a1/ |archive-date=28 February 2013 |website=TheFireArmBlog.com |date=24 February 2013}}</ref> The order was expected to be completed by 2018.<ref>{{cite web |url=http://www.strategicdefenceintelligence.com/article/htrM7sZtjw/2013/02/27/fn_manufacturing_to_deliver_m4m4a1_carbines_to_us_army/|title=FN Manufacturing to deliver M4/M4A1 Carbines to US Army |archive-url=https://web.archive.org/web/20130927142648/http://www.strategicdefenceintelligence.com/article/htrM7sZtjw/2013/02/27/fn_manufacturing_to_deliver_m4m4a1_carbines_to_us_army/ |archive-date=27 September 2013 |website=Strategic Defense Intelligence.com |date=27 February 2013}}</ref>

=== Replacement efforts ===
Replacements for the M4 have mostly focused on two factors: improving its reliability, and its penetration.{{Sfn|Rottman|2011|p=76}} The first attempt to find a replacement for the M4 came in 1986, with the [[Advanced Combat Rifle]] program, in which the [[Caseless ammunition|caseless]] [[Heckler & Koch G11]] and various [[Needlegun|flechette rifles]] were tested, but this was quickly dropped as these designs were mostly prototypes, which demonstrated a lack of reliability.{{Sfn|Rottman|2011|p=76}} In the 1990s, the [[Objective Individual Combat Weapon]] competition was put forth to find a replacement for the M4. Two designs were produced, both by [[Heckler & Koch]]: the [[XM29 OICW]], which incorporated a [[Smart munition|smart]] grenade launcher, but was canceled in 2004 as it was too heavy, and the [[Heckler & Koch XM8|XM8]], which was canceled in 2005 as it did not offer significant enough improvements over the M4.{{Sfn|Rottman|2011|p=76}}

The [[Heckler & Koch HK416]] was introduced in 2005, incorporating the same lower receiver as the M4A1, but replacing its direct impingement system with a gas-operated rotating bolt, more comparable to that of the [[Heckler & Koch G36|G36]].<ref>{{cite web|last=Moss|first=Matthew|date=2019-03-19|title=Meet Heckler & Koch's HK416: The Rifle You Need To Know About|url=https://nationalinterest.org/blog/buzz/meet-heckler-kochs-hk416-rifle-you-need-know-about-48057|access-date=2021-07-04|website=The National Interest|language=en}}</ref> The HK416 was adopted by the [[United States Navy SEALs|Navy SEALs]], [[Delta Force]], and other special forces.{{Sfn|Rottman|2011|p=76}} In 2010, it was adopted by the Marines as the M27 Infantry Automatic Rifle.<ref>{{cite web|last=Mizokami|first=Kyle|date=2017-04-04|title=The Marines Are in the Market For Brand New Rifles|url=https://www.popularmechanics.com/military/weapons/a25947/marines-replace-m4-rifle/|access-date=2021-07-04|website=Popular Mechanics|language=en-US}}</ref> The same year, the [[United States Army Rangers|Rangers]] and Navy SEALs adopted the [[FN SCAR]], but later withdrew their purchase, as it was not a significant enough improvement over the M4A1.{{Sfn|Rottman|2011|p=77}}

==== Individual Carbine ====
The U.S. Army briefly had a tender in 2011 called the [[Individual Carbine]], which solicited proposals for a potential M4 carbine replacement, but this was canceled in 2013 after determining that none of the entrants offered an adequate improvement over the M4.

For the Individual Carbine competition, Colt submitted their ''Enhanced M4'' design, also known as the [[Colt Advanced Piston Carbine]] (APC). The weapon has a suppression-ready fluted barrel, which is lighter and cools better than previous M4 barrels. It is claimed to have "markedly better" accuracy. To improve reliability, Colt used an articulating link piston (ALP), which "reduces the inherent stress in the piston stroke by allowing for deflection and thermal expansion".<ref>{{cite web |date=29 November 2011 |title=Enhanced M4 |url=http://www.defensereview.com/the-u-s-armys-next-carbine-hello-gas-pistonop-rod-enhanced-m4m4a1-carbine-type-ar-ar-15-goodbye-direct-gas-impingement-dgi-operation/ |archive-url=https://web.archive.org/web/20120521133807/http://www.defensereview.com/the-u-s-armys-next-carbine-hello-gas-pistonop-rod-enhanced-m4m4a1-carbine-type-ar-ar-15-goodbye-direct-gas-impingement-dgi-operation/ |archive-date=21 May 2012 |website=Defense Review}}</ref> In traditional [[Short-stroke piston|short-stroke gas piston]] operating systems designed for the AR platform, the force of the piston striking the bolt carrier can push the bolt carrier downwards and into the wall of the buffer tube, leading to accelerated wear and even chipped metal. This is known as [[carrier tilt]]. The ALP allows the operating rod to wiggle to correct for the downward pressure on the bolt and transfers the force straight backwards in line with the bore and buffer assembly, eliminating the carrier tilt. This relieves stress on parts and helps to increase accuracy.<ref>{{cite web |title=Colt's Advanced Piston Carbine, the LE6940P In Stores |url=http://www.investorvillage.com/smbd.asp?mb=2033&mn=64037&pt=msg&mid=11628448 |archive-url=https://web.archive.org/web/20131203203806/http://www.investorvillage.com/smbd.asp?mb=2033&mn=64037&pt=msg&mid=11628448 |archive-date=3 December 2013 |website=InvestorVillage.com}}</ref> The Individual Carbine competition was canceled before a winning weapon was chosen.<ref name="IC cancel"/>

==== Next Generation Squad Weapon ====
[[File:SIG Sauer XM5.png|thumb|SIG Sauer [[XM7]], caliber [[.277 Fury|6.8×51mm (.277 in)]]]]
After the failure of the Individual Carbine program, the [[Next Generation Squad Weapon]] (NGSW) was started in 2017. The program aimed to replace the M4 Carbine and the M249 SAW with weapons that would compensate for their perceived deficiencies when fighting at longer ranges, as well as addressing concerns about the effectiveness of traditional [[5.56×45mm NATO|5.56×45mm]] ammunition against troops wearing [[body armor]] in a future peer or near-peer conflict. In order to achieve these goals, all weapon submissions were to be chambered in a new 6.8x51 mm caliber. SIG Sauer, Textron Systems, FN Herstal, True Velocity (previously Lonestar Future Weapons and General Dynamics), and PCP Tactical took part in the program. Textron submitted a cased-telescoped (CT) ammunition-firing rifle for the program; FN Herstal submitted their [[HAMR IAR]] re-chambered in 6.8mm caliber; PCP Tactical submitted a modified [[Desert Tech MDR]]x; SIG Sauer submitted a redesigned [[SIG MCX|MCX]] variant known as the MCX-SPEAR. In early 2022, the program concluded, with [[SIG Sauer]] being declared the winner. Their rifle entry was designated the XM5 (later changed to [[XM7]] to avoid confusion with the Colt M5),<ref>{{Cite web |last=South |first=Todd |date=Jan 18, 2023 |title=New name selected for Army's Next Generation Squad Weapon |url=https://www.armytimes.com/news/your-army/2023/01/18/new-name-selected-for-armys-next-generation-squad-weapon/ |website=ArmyTimes}}</ref> and the [[XM250]] Squad Automatic Weapon.<ref>{{Cite web |last=Beynon |first=Steve |date=2022-04-19 |title=Army Picks Its Replacement for the M4 and SAW |url=https://www.military.com/daily-news/2022/04/19/army-picks-its-replacement-m4-and-saw.html |access-date=2022-05-04 |website=Military.com |language=en}}</ref> Operational testing and fielding were scheduled for 2024.

==Design==
[[File:Colt M4 MWS Carbine Iraq.jpg|thumb|right|M4 with [[Aimpoint CompM2|M68 Close Combat Optic]] and AN/PAQ-4]]

The M4, and its variants, is a lightweight [[5.56×45mm NATO]] (and [[.223 Remington]]) caliber, gas-operated, magazine-fed, air-cooled selective fire AR-15-pattern [[firearm]]. Its gas operation consists of an internal piston (often incorrectly referred to as [[direct impingement]]),<ref>{{Cite web |date=2024-02-04 |title=AR-15 Direct Impingement vs Piston Gas Systems: What's the Difference? - CAT Outdoors |url=https://catoutdoors.com/direct-impingement-vs-piston-gas-systems/ |access-date=2024-03-26 |language=en-US}}</ref> a rotating bolt, and bolt carrier that reciprocates into a receiver extension that is inline with the barrel. The gas system, bolt carrier, and bolt-locking design is ammunition specific, since it does not have an adjustable gas port or valve to adjust the weapon to various propellant and projectile or barrel length specific pressure behavior. The receiver is made of forged 7075-T6 aluminum, while the {{cvt|14.5|in|mm|adj=on|0}} barrel, bolt, bolt carrier, and fire control group are made of steel; these components can be easily serviced and replaced by unit armories, enabling the addition of enhanced components and thus making the platform readily upgradable. The flattop upper receiver's Picatinny rail enables the replacement of the removable carrying handle with various optics. The furniture, including the buttstock, grip, and handguard are made of reinforced plastic, although the modular nature of the weapon means that these can be swapped by the end user. The receiver extension can accommodate either a multi-position [[telescoping stock]] or a fixed A2 or LE tactical stock.{{efn|The first stock fitted onto the M4 in 1985 was made entirely of plastic, which only had two positions; fully closed or fully extended. Later models have greater adjustability, and are commonly known as the "six position stock", "M4 stock", or, because of its recesses, "waffle stock".{{Sfn|McNab|2021|p=10}}}}<ref>{{cite web |url=http://www.militarytimes.com/projects/flash/2007_02_20_carbine/ |title=Animation of the gas system of the M4 carbine |publisher=Militarytimes.com |access-date=2010-08-30 |url-status=dead |archive-url=https://web.archive.org/web/20091228092153/http://www.militarytimes.com/projects/flash/2007_02_20_carbine/ |archive-date=2009-12-28}}</ref> The M4 is a shorter and lighter variant of the M16A2 rifle, sharing much of the same operation mechanisms and has 80% parts commonality; the chief differences are a shorter barrel of 14.5 inches rather than 20 inches as well as a shortened receiver extension and buffer.<ref name="Design_SOC">{{cite web |url=http://www.specialoperations.com/Weapons/Features/M4/Page_Two.htm |title=The Design & Development of the M-4 Carbine |publisher=Special Operations.com |access-date=2008-11-08 |url-status=dead |archive-url=https://web.archive.org/web/20081025100813/http://www.specialoperations.com/Weapons/Features/M4/Page_Two.htm |archive-date=2008-10-25}}</ref>{{Sfn|McNab|2021|p=10}}

Two fire control groups exist for the M4 family, the three-round burst for the baseline model and fully automatic for the M4A1.<ref name="IC cancel"/> Some M4A1 may also have a heavier profile barrel initially developed for SOCOM for prolonged automatic fire; models with this heavier "SOCOM profile" barrel use the same M4A1 designation, and existing weapons can swap to the heavier profile barrel at the unit armory level. Despite being its namesake, SOCOM itself has reverted to the original lighter "government profile" barrel while adopting a longer "mid length" gas system with its newer Upper Receiver Group-Improved (URG-I) modifications. As the modifications only affect the upper receiver assembly, rifles with the URG-I still retain the M4A1 designation.<ref name="URGI_barrel_contract"/>

[[File:US- Solder.jpg|thumb|right|M4 with the newer, redesigned telescoping [[Stock (firearm)|stock]]]]
The M4's maneuverability makes it beneficial for non-infantry troops (vehicle crews, clerks and staff officers), as well as for [[Close Quarters Battle|close quarters battle]]. The M4, along with the M16A4, has mostly replaced the M16A2 in the Army and Marines. The [[United States Air Force|U.S. Air Force]], for example, has transitioned completely to the M4 for Security Forces squadrons, while other armed personnel retain the M16A2. The U.S. Navy uses M4A1s for Special Operations and vehicle crews. However, the M4's shorter barrel reduces its range, with its rear iron sights integrated in the (removable) carry handle only adjustable from {{convert|300|m|yard|0|abbr=on}} up to {{convert|600|m|yard|0|abbr=on}}, compared to the M16A2 rear iron sights integrated in the fixed carry handle, which can reach up to {{convert|800|m|yard|0|abbr=on}}.{{Sfn|McNab|2021|p=11}}

===Accessories===
[[File:Casing.jpg|thumb|right|M4A1 just after firing, with an ejected [[Cartridge (firearms)|case]] in mid-air; the [[M203 grenade launcher|M203]] and [[Aimpoint CompM2|M68 CCO]] are attached]]

Like all the variants of the M16, the M4 and the M4A1 can be fitted with many accessories, such as [[Sling (firearms)|slings]], [[night-vision device]]s, [[flash suppressor]]s, [[Silencer (firearms)|suppressors]], [[Laser sight (firearms)|laser sights]], [[telescopic sight]]s, [[bipod]]s, [[M9 bayonet]], either M203 or M320 grenade launcher, M26-MASS shotgun, [[Vertical forward grip|forward hand grips]], a detachable rail-mounted carrying handle, or anything else compatible with a MIL-STD-1913 [[picatinny rail]].{{Sfn|McNab|2021|pp=22-28}}

Other common accessories include the [[AN/PEQ-2]], [[AN/PEQ-15]] multi-mode laser, [[AN/PEQ-16|AN/PEQ-16 Mini Integrated Pointing Illumination Module (MIPIM)]], [[Trijicon]] TA01 and TA31 [[Advanced Combat Optical Gunsight]]s (ACOG), [[EOTech|EOTech 550 series]] holographic sights, and [[Aimpoint AB|Aimpoint]] [[Aimpoint CompM2|M68 Close Combat Optic]]. Visible and infrared lights of various manufacturers are commonly attached using various mounting methods. As with all versions of the M16, the M4 accepts a [[Blank-firing adaptor|blank-firing attachment]] (BFA) for training purposes.

The M4 and the M4A1 feed from 30-round [[STANAG magazine]]s.{{Sfn|McNab|2021|p=66}} Other types of STANAG compatible magazines with different capacities may also be used. In January 2017, a USMC unit deployed with suppressors mounted to every infantry M4 service weapon. Exercises showed that having all weapons suppressed improved squad communication and surprise during engagements; disadvantages included additional heat and weight, increased maintenance, and the greater cost of equipping so many troops with the attachment.<ref>{{cite web |url=http://www.military.com/daily-news/2017/05/11/marine-unit-norway-first-deploy-rifle-suppressors.html |title=Marine Unit in Norway First to Deploy with Rifle Suppressors|archive-url=https://web.archive.org/web/20170515162019/http://www.military.com/daily-news/2017/05/11/marine-unit-norway-first-deploy-rifle-suppressors.html |archive-date=15 May 2017 |website=[[Military.com]] |date=11 May 2017}}</ref> In July 2020, the Marine Corps announced it would be ordering suppressors for use by all M4 carbines used by close combat units.<ref>[https://www.military.com/daily-news/2020/07/13/marine-corps-plans-fielding-suppressors-infantry-squads-starting-year.html The Marine Corps Plans on Fielding Suppressors to Infantry Squads Starting this Year]. ''[[Military.com]]''. 13 July 2020.</ref> The Marines began to roll out suppressors for all M4/M4A1 carbines in infantry, reconnaissance and special operations units in December 2020.<ref>[https://www.marinecorpstimes.com/news/your-marine-corps/2020/12/30/marine-corps-to-start-widespread-distribution-of-suppressors/ Marine Corps to start widespread distribution of suppressors]. ''[[Marine Corps Times]]''. 31 December 2020.</ref>

==== Special Operations Peculiar Modification ====
[[File:SOPMOD 2-2005.jpg|thumb|left|SOPMOD (Special Operations Peculiar Modification) Block I]]

In 1992, [[United States Special Operations Command|U.S. Special Operations Command]] (USSOCOM) developed the Special Operations Peculiar Modification ([[SOPMOD]]) Block I kit for the carbines used by [[United States special operations forces|US Special Operations Forces]] units operating under its command.{{Sfn|McNab|2021|p=20}} The kit features an M4A1, a Rail Interface System (RIS) handguard developed by [[Knight's Armament Company]] (KAC), a shortened quick-detachable M203 grenade launcher and [[Sight (device)|leaf sight]], a KAC [[Silencer (firearm)|sound suppressor]], a KAC back-up rear sight, an Insight Technologies [[AN/PEQ-2]]A visible laser/[[infrared]] [[Laser designator|designator]], along with Trijicon's ACOG TA-01NSN model and [[Red dot sight|Reflex sights]], and a [[night vision device|night vision]] sight, among many other accessories.{{Sfn|McNab|2021|p=21}} This kit was designed to be configurable (modular) for various missions, and the kit is currently in service with special operations units.{{Sfn|McNab|2021|p=20}}

[[Image:SOPMOD Block I Phased replacements.png|thumb|right|SOPMOD Block II and Phased Replacements]]
In 2002, the Block II modification kit was adopted featuring two new upper receivers: the Special Purpose Receiver (SPR) with a {{cvt|16|or|18|in|mm|0}} barrel and [[Close Quarters Battle Receiver|Close Quarter Battle Receiver]] (CQBR) with a {{cvt|10.3|in|mm|0}} barrel.<ref>{{cite web|url=https://www.nsn-now.com/1005014981913 |title = 1005-01-498-1913, Receiver, Automatic Gun}}</ref>{{Sfn|McNab|2021|p=29}} M4A1s fitted with the SPR were designated by the Navy as the [[Mk 12 Special Purpose Rifle]], a type of [[designated marksman rifle]].{{Sfn|McNab|2021|p=29}} M4A1s with the CQBR were designated the Mk 18 Mod 0. The Block II program then focused on component improvements to the M4A1, with the adoption of the heavier "SOCOM profile" barrel in 2004 and free-float Rail Interface System II (RIS-II) handguard from [[Daniel Defense]] in 2008. Owing to the modularity of the AR-15/M4 platform, some operators have replaced issued optics, handguards, and buttstocks with aftermarket ones.{{Sfn|McNab|2021|p=29}}

In 2018, the Upper Receiver Group-Improved (URG-I) modification kit (unofficially the Block III) was approved for the conversion of Block I and Block II carbine's upper receiver "to an improved barrel and rail assembly.." which includes a lighter free-float handguard from Geissele Automatics that incorporates the [[Magpul Industries]] [[M-LOK]] rail interface system. The URG-I also replaces the Block II's heavier barrel with a standard "government profile" cold hammer forged barrel with a longer gas system.<ref>{{cite web|url=https://www.nsn-now.com/1005016713911|title = 1005-01-671-3911, Modification Kit, Gun, Weapon}}</ref>

==Variants==
{{Further|topic=M4 carbine variants|List of Colt AR-15 and M16 rifle variants}}

The initial order of M4 carbines had a fixed carrying handle and rear sight similar to the M16A2. The flattop upper receiver with the Picatinny rail was introduced with the M4A1 variant in 1994, and all subsequent orders for all M4 variants would have a flattop upper receiver. Variants of the carbine built by different manufacturers are also in service with many other foreign special forces units, such as the Australian [[Special Air Service Regiment]] (SASR). While the SASR uses weapons of essentially the same pattern built by Colt for export (Colt uses different models to separate weapons for the U.S. military and those for commercial/export purposes), the British [[Special Air Service]] uses a variant on the basic theme, the [[Colt Canada]] [[Colt Canada C7|C8SFW]].

===M4 MWS (Modular Weapon System)===
[[File:m4w-att.jpg|thumb|M4 MWS (Modular Weapon System) shown with various accessories including [[M203 grenade launcher]], RIS foregrip, removable carry handle/rear sight assembly, AN/PAQ-4 [[Laser sight (firearms)|laser system]], [[Aimpoint CompM2|M68 CCO]] reflex sight, and the [[AN/PVS-4]] night vision optics]]

Colt Model ''925'' carbines were tested and fitted with the KAC M4 RAS under the designation ''M4E2'', but this designation appears to have been scrapped in favor of mounting this system to existing carbines without changing the designation. The U.S. Army Field Manual specifies for the Army that adding the Rail Adapter System (RAS) turns the weapon into the ''M4 MWS'' or ''[[modular weapon system]]''.

===M4A1===
[[File:Coltm4a1.jpeg|thumb|M4A1 with a carry handle]]
[[File:M4A1 ACOG.png|thumb|M4A1 with [[Advanced Combat Optical Gunsight|TA01NSN ACOG]] 4×32 optical sight]]

The M4A1 carbine is a fully automatic variant of the basic M4 carbine. The M4A1 was developed in May 1991 and entered service in 1994; starting in 2014 the U.S. Army began upgrading all of its existing M4s to the M4A1 standard.<ref>{{cite web|url=https://www.thefirearmblog.com/blog/2020/03/20/us-army-continues-m4-modernization-program/|title="US Army Continues M4 Modernization Program"|first=Matthew|last=Moss|date=20 March 2020 }}</ref> The M4A1 was the first M4 model with the removable carry handle. The M4A1 has a "S-1-F" (safe/semi-automatic/fully automatic) trigger group, while the M4 has a "S-1-3" (safe/semi-automatic/3-round burst) trigger group. The M4A1 is used by almost all U.S. special operation units; and is the standard service rifle across the U.S. Army (including conventional forces). It has a maximum effective range of {{convert|500|to(-)|600|m|yd|sp=us}}.<ref name="Army_fact_file">{{cite news |date=June 2010 |title=Operators Manual for Carbine, 5.56 MM, M4A1 |pages=18 |work=TM 9-1005-213-10 |publisher=United States Army |url=https://mcarbo.americommerce.com/.Owners%20Manuals/tm-9-1005-319-10-2010-operator-s-manual-for-rifle-5.56-mm-m16a2-m16a3-m4-web.pdf |url-status=live |access-date=13 August 2023 |archive-url=https://web.archive.org/web/20221018003953/https://mcarbo.americommerce.com/.Owners%20Manuals/tm-9-1005-319-10-2010-operator-s-manual-for-rifle-5.56-mm-m16a2-m16a3-m4-web.pdf |archive-date=18 October 2022}}</ref> The fully automatic trigger gives a more consistent trigger pull, which leads to better accuracy.<ref name="IC cancel">{{cite news |url=http://www.military.com/daily-news/2013/06/13/army-kills-competition-to-replace-m4.html |title=Army Kills Competition to Replace M4|archive-url=https://web.archive.org/web/20130922093821/http://www.military.com/daily-news/2013/06/13/army-kills-competition-to-replace-m4.html?ESRC=sm_todayinmil.nl |archive-date=22 September 2013|work=Military.com |date=13 June 2013}}</ref> According to Mark Westrom, owner of [[ArmaLite|ArmaLite, Inc.]], automatic fire is better for clearing rooms than burst fire.<ref name="IC history">{{cite news |url=http://www.nationaldefensemagazine.org/archive/2013/August/Pages/CarbineCompetitionFailstoFindImprovementOverCurrentWeapon.aspx |title=Carbine Competition Fails to Find Improvement Over Current Weapon|archive-url=https://web.archive.org/web/20151018065606/http://www.nationaldefensemagazine.org/archive/2013/August/Pages/CarbineCompetitionFailstoFindImprovementOverCurrentWeapon.aspx |archive-date=18 October 2015 |work=National Defense Magazine|date=August 2013}}</ref>

A subvariant of the M4A1 uses a heavier barrel than the standard M4, as the regular M4 barrel, which can fire 6,000 rounds before requiring inspection for possible replacement,{{Sfn|McNab|2021|p=47}} was not sufficient for the higher consumption of ammunition by SOCOM operators.{{Sfn|McNab|2021|p=16}} The redesigned barrel, colloquially referred to as the "SOCOM barrel", has an increased [[diameter]] in the area between the receiver and front sight.{{Sfn|McNab|2021|p=16}} Despite the different barrel profile, this subvariant did not receive a new designation, and was still referred to as the M4A1. Ironically, SOCOM itself would dispense with its namesake heavier barrel and return to the original "government profile" with its Upper Receiver Group-Improved (URG-I) program's mid-length gassed, cold hammer forged barrels.<ref name="URGI_barrel_contract">{{cite web |title=Request for Information (RFI)/Sources Sought – Upper Receiver Group – Improved (URG-I) Cold Hammer Forged (CHF) 11. 5" Carbine Length and 14. 5" Mid-Length Barrels |url=https://govtribe.com/opportunity/federal-contract-opportunity/request-for-information-rfisources-sought-upper-receiver-group-improved-urg-i-cold-hammer-forged-chf-11-dot-5-carbine-length-and-14-dot-5-mid-length-barrels-n0016420snb73 |work=Department of Defense |date=13 July 2020}}</ref><ref>{{cite web |url=https://www.militarytimes.com/off-duty/gearscout/2018/10/03/this-new-upper-receiver-is-the-closest-you-can-get-to-owning-one-of-usasocs-high-speed-m4s/ |title=This new upper receiver is the closest you can get to owning one of USASOC's high-speed M4s |work=Military Times |date=3 October 2018}}</ref>

===Mk 18 CQBR===
[[File:CQBR-alone.png|thumb|right|M4A1 lower receiver with a Mk 18 Close Quarter Battle Receiver upper. The barrel length is {{cvt|10.3|in}}]]
{{Main|Close Quarters Battle Receiver}}

The ''Close Quarters Battle Receiver'' (CQBR) was originally a Special Operations Peculiar Modification (SOPMOD) program item that would increase the close quarters maneuverability of the M4A1 by mating the lower receiver with a {{convert|10.3|in|0|adj=on}} barreled upper receiver; with the CQBR installed, the weapon would then be classified as the ''Mk. 18 CQBR''. The Mk. 18 CQBR may be issued as a standalone complete weapon system to SOCOM personnel, or as a separate upper receiver for their M4A1 to enable greater mission flexibility.<ref>{{cite web|last=Johnson|first=Jeff|title=CQB Receiver – M4A1 Carbine with 10-Inch Upper Receiver|url=https://www.scribd.com/doc/52753307/CQBR|website=Scribd.com |format=Power point presentation|publisher=US Naval Surface Warfare Center Crane|access-date=2 May 2012|archive-url=https://web.archive.org/web/20111104110631/http://www.scribd.com/doc/52753307/CQBR|archive-date=4 November 2011|url-status=live|df=mdy-all}}</ref>

===Mk 12 SPR===
{{Main|Mk 12 Special Purpose Rifle}}
[[File:SPRCrane.jpg|thumb|A Special Purpose Receiver built by NWSC Crane Division, mounted on an M16A1 lower receiver]]

The SOPMOD program also introduced the ''Special Purpose Receiver'' (SPR), a {{cvt|16|or|18|in|mm|0|adj=on}} barreled upper receiver that would be mated to an M4A1 lower receiver to allow the weapon to serve as a designated marksman rifle (DMR). Although originally intended as an upper receiver kit for the M4A1 like the CQBR, the SPR would eventually be issued as a standalone complete rifle designated the ''Mk. 12 Special Purpose Rifle'', with some assembled from M4A1 lower receivers.

===SOPMOD Block II===
[[File:Flickr - DVIDSHUB - Operation in Nahr-e Saraj (Image 5 of 7).jpg|thumb| M4A1s in SOPMOD Block II used by 2 [[75th Ranger Regiment]] operators clearing a room during a night raid in [[Helmand Province]], Afghanistan, 2012]]

The ''SOPMOD Block II'' is a more radical modification kit for the baseline M4A1 that can be fitted at first-echelon unit maintenance level. Components of the Block II were phased in gradually, but the most distinctive feature is the [[free-floating barrel|free-floated]] Daniel Defense Rail Interface System II (RIS II), first issued in 2008. The RIS II is available in 9.5 inches for the Mk 18 Mod 1 or 12.5 inches for the M4A1. Other components of the Block II include the L3 Advanced Target Pointer Illuminator Aiming Laser (ATPIAL), or the [[AN/PEQ-15]] as well as the LA5 high-power variants, and the ELCAN SpecterDR 1-4 optic.

===Upper Receiver Group-Improved (URG-I)===
[[File:The Quiet Professionals 191014-M-UB217-421.jpg|thumb|The URG-I used by one of the [[United States Army Special Forces|Green Berets]] from [[3rd Special Forces Group (United States)|3rd SFG (A)]] with a black Magpul PMAG during training at [[Marine Corps Air Ground Combat Center]], [[Twentynine Palms, California|Twentynine Palms]], [[California]] in 2019]]

The ''Upper Receiver Group-Improved'' (URG-I) is a [[United States Army Special Operations Command|U.S. Army Special Operations Command]] (USASOC) program to further improve the durability and reliability of the SOPMOD Block II by introducing additional component improvements. First fielded in 2018, the main improvements are the lighter Geissele Mark 16 free-float rail that incorporates [[M-LOK]] as the mounting method and a Daniel Defense cold hammer-forged barrel that returns to the lighter "government" profile contour as well as a mid-length gas system. Although initially an Army program, the URG-I has seen use by other components of SOCOM as well.

===GAU-5/A===
The ''GAU-5/A'' Aircrew Self Defense Weapon (ASDW) is an Air Force modified M4 with a detachable barrel and handguard assembly, folding pistol grip, and fold-down iron sights to enable compact packaging. This weapon is stowed in [[ejection seat]]s of tactical aircraft and is intended to allow [[aircrew]] who egress in hostile environments to better defend themselves until rescue than existing handguns. The weapons entered service in 2018.<ref>{{cite news |url=https://www.thedrive.com/the-war-zone/27950/usaf-fighter-pilots-are-now-flying-with-these-converted-m4-rifles-in-their-survival-kits |title=USAF Fighter Pilots Are Now Flying With These Converted M4 Rifles In Their Survival Kits |work=The War Zone |date=10 May 2019 |first1=Joseph |last1=Trevithick}}</ref> Confusingly, this weapon shares the same designation as the Air Force [[CAR-15]] variant in service since 1966.<ref>{{cite news |url=https://www.thedrive.com/the-war-zone/21867/usaf-fighter-and-bomber-crews-get-modified-m4-rifles-that-fit-under-ejection-seats |title=USAF Fighter And Bomber Crews Get Modified M4 Rifles That Fit Under Ejection Seats |work=The War Zone |date=5 June 2019 |first1=Joseph |last1=Trevithick}}</ref>

==Performance==
[[File:US Navy SEAL team member in Afghanistan 2002.jpg|thumb|A [[U.S. Navy SEAL]] with an M4 during counterterrorism operations in Afghanistan, January 2002]]
The M4 carbine has been used for close quarters operations where the [[M16 rifle|M16]] would be too long and bulky to use effectively. It has been a compact, light, customizable, and accurate weapon. Like other firearms, failure to properly maintain the M4 can result in malfunctions. This became apparent as it saw continued use in the sandy environments of [[Iraq War|Iraq]] and [[War in Afghanistan (2001–present)|Afghanistan]].<ref>{{cite web |url=http://www.defenseindustrydaily.com/the-usas-m4-carbine-controversy-03289/|title=M4 Carbine Controversy |archive-url=https://web.archive.org/web/20070713081000/http://www.defenseindustrydaily.com/the-usas-m4-carbine-controversy-03289/ |archive-date=13 July 2007 |website=Defense Industry Daily}}</ref> Despite this, in post-combat surveys, 94% of soldiers rated the M4 as an effective weapons system.<ref>{{cite web |url=https://fas.org/man/dod-101/sys/land/wsh2012/294.pdf |title=Small Arms-Individual Weapons |access-date=4 April 2015 |archive-url=https://web.archive.org/web/20171212062921/https://fas.org/man/dod-101/sys/land/wsh2012/294.pdf |archive-date=12 December 2017 |url-status=live}}</ref>

===2006 CNA report===
In December 2006, the [[CNA (nonprofit)|Center for Naval Analyses]] (CNA) released a report on U.S. small arms in combat. The CNA conducted surveys on 2,608 troops returning from combat in Iraq and Afghanistan over the previous 12 months. Only troops who fired their weapons at enemy targets were allowed to participate. 917 troops were armed with M4 Carbines, making up 35% of the survey. 89% of M4 users reported they were satisfied with the weapon. 90% were satisfied with handling qualities such as handguards, size, and weight. M4 users had the highest levels of satisfaction with weapon performance, including 94% with accuracy, 92% with range, and 93% with rate of fire. Only 19% of M4 users reported a stoppage, and 82% of those that experienced a stoppage said it had little impact on their ability to clear the stoppage and re-engage their target. The lowest rated weapon was the M9, and the [[M249 light machine gun|M249]] had the highest rate of stoppages.{{Sfn|McNab|2021|p=68}} 53% of the M4 users never experienced failures of their magazines to feed. 81% did not need their rifles repaired while in theater. 80% were confident in the M4's reliability, defined as confidence their weapon will fire without malfunction, and 83% were confident in its durability, defined as confidence their weapon will not break or need repair. Both factors were attributed to high levels of soldiers performing their own maintenance. 54% of M4 users offered recommendations for improvements. 20% of requests were for greater bullet lethality, and 10% were for better quality magazines, as well as other minor recommendations. Only 75% of M16 users were satisfied with it,{{Sfn|McNab|2021|p=67}} and some expressed their desire to be issued the M4.<ref>{{cite web |url=http://images.military.com/pix/defensetech/cna_m4_study_d0015259_a2.pdf |title=Soldier Perspectives on Small Arms in Combat|website=CNA Corporation |publisher=Department of Defense|archive-url=https://web.archive.org/web/20150831150054/http://images.military.com/pix/defensetech/cna_m4_study_d0015259_a2.pdf |archive-date=31 August 2015 |author1=Russell, Sara M.|date=2006}}</ref> Some issues from this report have been addressed with the issuing of the [[STANAG magazine#Issues and improvements|improved STANAG magazine]] in March 2009,<ref name="stanagmag1">{{cite web |url=http://www.thefirearmblog.com/blog/2009/06/13/brownells-shipping-m16-magazines-with-anti-tilt-follower-to-military/ |title=Brownells shipping M16 magazines with anti-tilt follower to military |archive-url=https://web.archive.org/web/20130921053406/http://www.thefirearmblog.com/blog/2009/06/13/brownells-shipping-m16-magazines-with-anti-tilt-follower-to-military/ |archive-date=21 September 2013 |website=The Firearm Blog |date=13 June 2009}}</ref><ref name="stanagmag2">{{cite news |url=http://www.thefirearmblog.com/blog/2009/12/16/new-us-army-m16-tan-magazine/|title=New US Army M16 "Tan" Magazine |archive-url=https://web.archive.org/web/20130921053924/http://www.thefirearmblog.com/blog/2009/12/16/new-us-army-m16-tan-magazine/ |archive-date=21 September 2013 |website=The Firearm Blog |date=16 December 2009}}</ref> and the [[5.56×45mm NATO#M855A1|M855A1 Enhanced Performance Round]] in June 2010.<ref>{{cite web |url=http://www.pica.army.mil/PicatinnyPublic/highlights/archive/2010/06-24-10.asp |title=Army begins shipping improved 5.56mm cartridge|archive-url=https://web.archive.org/web/20130601185932/http://www.pica.army.mil/PicatinnyPublic/highlights/archive/2010/06-24-10.asp |archive-date=1 June 2013 |website=Picatinny Arsenal |date=24 June 2010}}</ref>

===2007 dust test===
In summer and fall 2007, the Army tested the M4 against three other carbines in "[[Dust storm|sandstorm]] conditions" at [[Aberdeen Proving Ground]], [[Maryland]]: the [[Heckler & Koch]] [[Heckler & Koch XM8|XM8]], [[FN Herstal|Fabrique Nationale de Herstal]] [[FN SCAR|SOF Combat Assault Rifle]] (SCAR) and the Heckler & Koch HK416. Ten of each type of rifle were used to fire 6,000 rounds each, for a total of 60,000 rounds per rifle type.<ref>{{cite web |url=http://www.military.com/NewsContent/0,13319,158468,00.html |first=Christian |last=Lowe |title=M4 Carbine Fares Poorly in Dust Test |publisher=Military Advantage |work=Military.com |date=2007-12-18 |access-date=2008-09-13 |archive-url=https://web.archive.org/web/20080813020030/http://www.military.com/NewsContent/0,13319,158468,00.html |archive-date=2008-08-13 |url-status=live}}</ref> The M4 suffered far more stoppages than its competitors: 882 stoppages, 19 requiring an armorer to fix. The XM8 had the fewest stoppages, 116 minor stoppages and 11 major ones, followed by the FN SCAR with 226 stoppages and the HK416 with 233.<ref>{{cite web|url=http://www.defensetech.org/archives/003909.html |title=...And Here's the Rest of the M4 Story |publisher=Military Advantage |work=Defense Tech |date=2007-12-18 |access-date=2008-09-13 |url-status=usurped |archive-url=https://web.archive.org/web/20071223084812/http://www.defensetech.org/archives/003909.html |archive-date=2007-12-23}}</ref><ref>{{cite web |url=http://www.armytimes.com/news/2007/12/army_carbine_dusttest_071217/ |first=Matthew |last=Cox |title=Newer carbines outperform M4 in dust test |work=Army Times |publisher=Army Times Publishing Company |date=2007-12-19 |archive-url=https://archive.today/20120630044756/http://www.armytimes.com/news/2007/12/army_carbine_dusttest_071217/ |archive-date=2012-06-30 |access-date=2019-07-24 |url-status=dead}}</ref>

Despite 863 minor stoppages—termed "class one" stoppages, which require 10 seconds or less to clear, or "class two" stoppages, which require more than ten seconds to clear—the M4 functioned well, with over 98% of the 60,000 total rounds firing without a problem. The Army said it planned to improve the M4 with a new [[Berlin-Lübecker Maschinenfabrik#Innovation|cold-hammer-forged]] barrel to give longer life and more reliable magazines to reduce the stoppages. Magazine failures caused 239 of the M4's failures. Army officials said the new magazines could be combat-ready by spring if testing went well.<ref>{{cite web |url=http://www.armytimes.com/news/2007/12/army_m4_hearing_071217w/ |title=M4 may get tougher barrel, better mags |first=Matthew |last=Cox |work=Army Times |publisher=Army Times Publishing Company |date=2007-12-17 |archive-url=https://archive.today/20120721112846/http://www.armytimes.com/news/2007/12/army_m4_hearing_071217w/ |archive-date=2012-07-21 |access-date=2019-07-24 |url-status=dead}}</ref> The Army began issuing an improved STANAG magazine in March 2009.<ref name="stanagmag1"/><ref name="stanagmag2"/>

According to the Army, the M4 only suffered 296 stoppages and said that the high number reported could be attributed to discrepancies in the scoring process. The Army testing command stated that, if the number of stoppages caused by a broken part met some threshold, they would be eliminated from the final report pending redesign of the part. The [[methodology]] of the test has been debated, as many of the M4s in the test had already seen use, whereas the other rifles were brand new, and that the wide variance in results between summer and fall showed that the test was not accurate, as it was not repeatable with consistent results.{{Sfn|McNab|2021|p=73}} Furthermore, the trial M4s had burst-mode fire groups, which are more complicated and prone to failure than the fully automatic fire groups the other manufacturers presented for testing.<ref>{{cite web |url=https://fas.org/sgp/crs/weapons/RS22888.pdf |title=The Army's M4 Carbine: Background and Issues for Congress|archive-url=https://web.archive.org/web/20150323153156/http://www.fas.org/sgp/crs/weapons/RS22888.pdf |archive-date=23 March 2015 |website=Fas.org|date=8 June 2010}}</ref>

There were three extreme dust tests performed in 2007. The second test results showed a large difference from the last test with the M4 having 148 class 1 stoppages caused by rifle malfunctions and 148 class 1 stoppages caused by magazine stoppages. The full-size M16 rifle had 61 stoppages during the same extreme dust test.<ref>Combat Tactics Fall 2008 Volume Six Number Two "True Grit" by David Crane</ref>

===Reliability===
[[File:US Navy 080725-N-4236E-391 Fire Controlman Seaman Rachel Hubley fires an M4 carbine from the fantail of the guided-missile cruiser USS Vella Gulf (CG 72).jpg|thumb|A U.S. Navy sailor fires an M4 carbine from the warship {{USS|Vella Gulf|CG-72|6}}]]

In early 2010, two journalists from the ''[[New York Times]]'' spent three months with soldiers and Marines in Afghanistan. While there, they questioned around 100 infantrymen about the reliability of their M4 carbines, as well as the M16 rifle. Troops did not report reliability problems with their rifles. While only 100 troops were asked, they fought at least a dozen intense engagements in [[Helmand Province]], where the ground is covered in fine powdered sand (called "moon dust" by troops) that can stick to firearms. Weapons were often dusty, wet, and covered in mud. Intense firefights lasted hours with several magazines being expended. Only one soldier reported a jam when his M16 was covered in mud after climbing out of a [[canal]]. The weapon was cleared and resumed firing with the next chambered round. Furthermore, a Marine chief warrant officer reported that there were no issues with his [[battalion]]'s 700 M4s and 350 M16s.<ref>{{cite news |author1=Chivers, C.J.|url=http://atwar.blogs.nytimes.com/2010/07/07/examining-the-complaints-about-american-rifle-reliability/?_r=0 |title=Examining the Complaints About American Rifle Reliability |archive-url=https://web.archive.org/web/20130922150652/http://atwar.blogs.nytimes.com/2010/07/07/examining-the-complaints-about-american-rifle-reliability/?_r=0 |archive-date=22 September 2013|url-status=live |work=The New York Times|date=7 July 2010|df=mdy-all}}</ref>

The reliability of the M4 has increased as the design was upgraded. In 1990, the M4 was required to fire 600 mean rounds between stoppages using M855 ammunition. In 2013, the current M4A1 version can fire 1,691 mean rounds between stoppages using M855A1 ammunition.<ref>{{cite news |url=http://www.military.com/daily-news/2013/06/14/army-gun-makers-didnt-meet-reliability-standard.html|title=Army: Gun Makers Didn't Meet Reliability Standard|archive-url=https://web.archive.org/web/20140427082315/http://www.military.com/daily-news/2013/06/14/army-gun-makers-didnt-meet-reliability-standard.html?ESRC=sm_todayinmil.nl |archive-date=27 April 2014 |work=Military.com |date=14 June 2013|author1=Cox, Matthew|url-status=live|df=mdy-all}}</ref> During the 2009 Marine Corps Infantry Automatic Rifle testing, the Colt IAR displayed a MRBS of CLASS I/II Stoppages of 952 rounds, with a MRBEFF (Mean Rounds Between Essential Function Failure) of Class III Stoppages of 60,000 rounds.<ref>{{cite web |url=http://weaponsman.com/?p=40433 |title=USMC IAR Reliability Testing Results |archive-url=https://web.archive.org/web/20170412062530/http://weaponsman.com/?p=40433 |archive-date=12 April 2017 |date=2009 |website=Weaponsman |url-status=dead|df=mdy-all}}</ref>

===Gas piston===
An array of firearms accessory makers have offered gas piston conversion kits for the M4. The claimed benefits include less needed lubrication for the [[Bolt (firearms)|bolt carrier group]] to run reliably and reduced fouling. The argument against it is increased weight and reduced accuracy.<ref name="Upgrade">{{cite web |title=Best AR-15 Piston Uppers & Conversion Kits [2019] |url=https://www.pewpewtactical.com/best-ar-15-piston-uppers-conversion-kits/ |website=Pew Pew Tactical |date=October 14, 2017}}</ref> The Enhanced M4 uses an articulating link piston operating system. Complicating the Army search for higher reliability in the M4 is a number of observations of M4 gas piston alternatives that suffer unintended design problems. The first is that many of the gas piston modifications for the M4 isolate the piston so that piston jams or related malfunction require the entire weapon be disassembled, such disassembly cannot be performed by the end-user and requires a qualified armorer to perform out of field, whereas almost any malfunction with the direct-impingement system can be fixed by the end-user in field. The second is that gas piston alternatives use an off-axis operation of the piston that can introduce carrier tilt, whereby the bolt carrier fails to enter the buffer tube at a straight angle, resulting in part wearing. This can also tilt the bolt during extraction, leading to increased bolt lug failures. The third is that the use of a sound suppressor results in hot gases entering the chamber, regardless of a direct-gas impingement or gas piston design choice. The gas piston system may also cause the firearm to become proprietary to the manufacturer, making modifications and changes with parts from other manufacturers difficult.<ref name="Direct Impingement Myth" /><ref>{{cite web |url=http://images.military.com/pix/defensetech/cna_m4_study_d0015259_a2.pdf |title=15259frcov.fm |access-date=2010-08-30 |url-status=dead |archive-url=https://web.archive.org/web/20150831150054/http://images.military.com/pix/defensetech/cna_m4_study_d0015259_a2.pdf |archive-date=2015-08-31}}</ref>

=== Accuracy ===
In a study conducted by the [[United States Army Marksmanship Unit|Army Marksmanship Unit]], they found that at a distance of {{cvt|300|yard|m}}, the M16 achieved a {{cvt|24|in|mm}} [[Shot grouping|grouping]], and the M4 achieved a {{convert|32|in|mm|abbr=on}} grouping, which dropped to {{cvt|12|in|mm}} and {{cvt|18|in|mm}} respectively when using [[match grade]] ammunition.{{Sfn|McNab|2021|p=37}} As the average male torso is {{cvt|18-19|in|mm}} wide, author Chris McNab concluded that this meant the M4 can be consistently accurate up to 300 yards, and noted that the frequent usage of optical attachments meant it could be accurate to higher ranges.{{Sfn|McNab|2021|p=37}}

=== ArmWest, LLC modified M4 ===
In 2014, American firearms designer [[Leroy James Sullivan|Jim Sullivan]] provided a video interview regarding his contributions to the M16 and M4 family of rifles while working for Armalite. A noted critic of the M4, he illustrates the deficiencies found in the rifle in its current configuration. In the video, he demonstrates his "ArmWest, LLC modified M4", with enhancements he believes necessary to rectify the issues with the weapon. Proprietary issues aside, the weapon is said to borrow features in his prior development, the [[Ultimax 100|Ultimax]]. Sullivan has stated (without exact details as to how) the weapon can fire from the closed bolt in semi-automatic and switch to open bolt when firing in fully automatic, improving accuracy. The weight of the cyclic components of the gun has been doubled (while retaining the weapon's weight at less than 8 pounds). Compared to the standard M4, which in automatic fires 700–950 rounds a minute, the rate of fire of the ArmWest, LLC M4 is heavily reduced both to save ammunition and reduce barrel wear. The reduced rate also renders the weapon more controllable and accurate in automatic firing.<ref name="Full30">{{cite web |date=26 November 2014 |title=Interview & Shooting: Jim Sullivan, AR-15 Designer |url=https://www.full30.com/video/9b50f8a825ab510b4c227c7b32a76bc1 |archive-url=https://web.archive.org/web/20150228202926/https://www.full30.com/video/9b50f8a825ab510b4c227c7b32a76bc1 |archive-date=2015-02-28 |website=Full30: INRANGE TV}}</ref>

==Manufacturers==
*[[Colt's Manufacturing Company]], US
*[[Remington Arms Company]], US<ref>{{cite web |title=R4 Complete System |url=https://www.remingtondefense.com/carbines/r4/operator/86612.html |website=Remington Defense |access-date=18 February 2021 |archive-date=14 December 2020 |archive-url=https://web.archive.org/web/20201214034001/https://www.remingtondefense.com/carbines/r4/operator/86612.html |url-status=dead }}</ref>
*[[FN Herstal]], Belgium<ref name="FN America">{{cite web |title=M4A1 |url=https://fnamerica.com/products/rifles/fn-m4a1/ |website=FN America |access-date=18 February 2021}}</ref>
*[[SME Ordnance]], Malaysia<ref name="Rifle">{{cite web|url=http://www.thestar.com.my/news/story.asp?file=/2007/11/5/nation/19381084&sec=nation |archive-url=https://web.archive.org/web/20081003114011/http://thestar.com.my/news/story.asp?file=%2F2007%2F11%2F5%2Fnation%2F19381084&sec=nation |url-status=dead |archive-date=2008-10-03 |title=Malaysia has licence to make M4 assault rifles |access-date=2010-03-22 |date=2007-11-05 |work=[[The Star (Malaysia)|The Star]]}}</ref>
*[[Sarsılmaz Arms|Sarsılmaz]], Turkey<ref name="Colt"/>
*[[United Defense Manufacturing Corporation]], Philippines

==Trademark issues==
The M4 was developed and produced for the [[Federal government of the United States|United States government]] by Colt Firearms, which had an exclusive contract to produce the M4 family of weapons through 2011.<ref>{{cite web|url=https://caselaw.findlaw.com/us-1st-circuit/1173327.html|title=FindLaw's United States First Circuit case and opinions.|website=Findlaw|access-date=2016-08-09|archive-url=https://web.archive.org/web/20160829053245/http://caselaw.findlaw.com/us-1st-circuit/1173327.html|archive-date=2016-08-29|url-status=live}}</ref> However, a number of other manufacturers offer M4-like firearms. Colt previously held a U.S. [[trademark]] on the term "M4".<ref>US Trademark serial number 76335060 registration number 2734001</ref> Many manufacturers offer production firearms that are essentially identical to a military M4, but with a {{convert|16|in|cm|adj=on}} barrel. The [[Bushmaster M4 Type Carbine]] is a popular example. Civilian models are sometimes colloquially referred to as "M4gery" ({{IPAc-en|ɛ|m|ˈ|f|ɔər|dʒ|ər|i}} {{respell|em|FOR|jə|ree}}, a [[portmanteau]] of "M4" and "forgery."){{Sfn|Rottman|2011|p=75}} Colt had maintained that it retained sole rights to the M4 name and design, while other manufacturers had long maintained that Colt had been overstating its rights, and that "M4" had now become a generic term for a shortened AR-15.{{Citation needed|date=May 2021}}

In April 2004, Colt filed a lawsuit against Heckler & Koch and [[Bushmaster Firearms, Inc.|Bushmaster Firearms]], claiming acts of [[trademark infringement]], [[trade dress]] infringement, [[trademark dilution]], false designation of origin, [[false advertising]], [[patent infringement]], [[unfair competition]], and deceptive trade practices. Heckler & Koch later settled out of court, changing one product's name from "HK M4" to "[[HK416]]". However, on December 8, 2005, a district court judge in [[Maine]] granted a [[summary judgment]] in favor of Bushmaster Firearms, dismissing all of Colt's claims except for false advertising. On the latter claim, Colt could not recover monetary damages. The court also ruled that "M4" was now a generic name and that Colt's trademark should be revoked.{{Sfn|Rottman|2011|p=75}}

==Users==
<!-- READ FIRST: This section is for cited entries only. Please do not add entries into this list without a citation from a reliable source. All entries without a citation will be removed. Thank you.
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[[File:M4 Carbine Users.png|thumb|A map with nations that use the M4 Carbine in blue]]

* {{Flag icon|Islamic Emirate of Afghanistan}} [[Afghanistan]]: Former Afghan National Army commando stocks in use by the [[Taliban]].<ref>{{Cite news|url=https://www.reuters.com/world/asia-pacific/taliban-takes-over-some-swap-iconic-ak-47s-made-in-america-rifles-2021-08-17/|title=As Taliban takes over, some swap iconic AK-47s for made-in-America rifles|newspaper=Reuters|date=17 August 2021|last1=Kelly|first1=Tim}}</ref>
* {{flag|Albania}}: Used by [[Albanian Armed Forces|Albanian Land Force]] 2015.<ref name="Gazeta Tema">{{cite web|url=http://www.gazetatema.net/web/2015/10/22/fotot-ushtria-shqiptare-tregon-dhembet/|title=FOTOT/ Ushtria shqiptare tregon "dhëmbët"|work=Gazeta Tema|access-date=2016-01-06|archive-url=https://web.archive.org/web/20151223124550/http://www.gazetatema.net/web/2015/10/22/fotot-ushtria-shqiptare-tregon-dhembet/|archive-date=2015-12-23|url-status=dead}}</ref>
* {{flag|Antigua and Barbuda}}: M4/M4A1s announced to be sold via FMS program in 2017.<ref name="FB"/>
* {{flag|Argentina}}: Used by [[Argentine Army]], [[Argentine Navy]] and [[Argentine National Gendarmerie]]<ref name="FB"/>
* {{flag|Australia}}: M4A1 (designated '''M4A5'''), used by [[Special Operations Command (Australia)|Special Operations Command]], [[Clearance Diving Team (RAN)|Clearance Divers]], and [[Police Tactical Group]]s.<ref>{{cite web |url=http://www.defencejobs.gov.au/navy/technology/clearanceDivers/maritimeTactical.aspx|title=Clearance Divers, Maritime Tactical Operations |archive-url=https://web.archive.org/web/20101102031512/http://www.defencejobs.gov.au/navy/technology/clearanceDivers/maritimeTactical.aspx |archive-date=2010-11-02 |website=Australian Defence Jobs|access-date=2011-09-27}}</ref>
*{{flag|Azerbaijan}}: M4 Carbine used by the special military units and State Border Service (DSX).<ref>{{cite web|url=https://aqreqator.az/az/siyaset/862891|title = DSX silahlanmasında ABŞ istehsalı tüfəng - M16 (ARAŞDIRMA)}}</ref>
* {{flag|Bahrain}}: M4A1s sold as a 2008 Foreign Military Sales package.<ref name="Guns 2008"/> More M4/M4A1s announced to be sold via FMS program in 2017.<ref name="FB">{{cite web|url=http://www.thefirearmblog.com/blog/2017/04/27/colt-capitalizes-foreign-military-sales-program/|title=Colt Capitalizes on Foreign Military Sales Program - The Firearm Blog|date=27 April 2017|access-date=1 May 2017|archive-url=https://web.archive.org/web/20170601061415/http://www.thefirearmblog.com/blog/2017/04/27/colt-capitalizes-foreign-military-sales-program|archive-date=1 June 2017|url-status=dead}}</ref>
* {{flag|Belize}}: M4s/M4A1s sold as part of a 2006 Foreign Military Sales package.<ref name="Guns 2006">{{cite web|author=Watters, Daniel|title=The 5.56 X 45mm: 2006|url=http://www.thegunzone.com/556dw-16.html|url-status=dead|archive-url=https://web.archive.org/web/20110301114359/http://www.thegunzone.com/556dw-16.html|archive-date=2011-03-01|access-date=2009-03-25}}</ref> More M4/M4A1s announced to be sold via FMS program in 2017.<ref name="FB"/>
* {{flag|Bosnia & Herzegovina}}: M4A1s used by the military and air guard units.<ref name="Guns 2008"/>
* {{flag|Bolivia}}: M4s used by [[UMOPAR]] and GTIDE units of the [[Bolivian National Police|Policia Nacional.]] M4A1 in use with rangers.<ref>{{Cite web |date=2016-11-24 |title=wiw_sa_bolivia |website=worldinventory |url=https://sites.google.com/site/worldinventory/wiw_sa_bolivia |access-date=2023-05-07 |archive-date=24 November 2016 |archive-url=https://web.archive.org/web/20161124203425/https://sites.google.com/site/worldinventory/wiw_sa_bolivia |url-status=bot: unknown }}</ref>
* {{flag|Brazil}}: Used by [[Civil Police (Brazil)|Civil Police]], [[Military Police of Espirito Santo State]], [[Military Police of Rio de Janeiro State]],<ref>{{cite web |url=http://www.policiamilitar.rj.gov.br/armas_veiculos.php|title=PMERJ |website=Polícia Militar do Estado do Rio de Janeiro |archive-url=https://web.archive.org/web/20140607054441/http://www.policiamilitar.rj.gov.br/armas_veiculos.php|archive-date=7 June 2014}}</ref> the [[Federal Police Department|Brazilian Federal Police]] and [[Special Forces]] of the [[Brazilian Army]], [[Brazilian Navy]].<ref>{{cite web|url=http://www.jusbrasil.com.br/diarios/38461016/dou-secao-3-05-07-2012-pg-28|title=DOU 05/07/2012 - Pg. 28 - Seção 3 - Diário Oficial da União - Diários JusBrasil|work=JusBrasil|access-date=15 November 2014|archive-url=https://web.archive.org/web/20141129035431/http://www.jusbrasil.com.br/diarios/38461016/dou-secao-3-05-07-2012-pg-28|archive-date=29 November 2014|url-status=live}}</ref>
* {{flag|Croatia}}: User since 2003, several hundred purchased for [[Croatian Army#Assault rifles|Croatian ISF]] contingent as well as [[Special Forces Command (Croatia)|Special Forces]].<ref>{{cite web |url=http://img268.imageshack.us/img268/6152/309767.jpg|title=Croatian special forces with M4s |archive-url=https://web.archive.org/web/20110717181118/http://img268.imageshack.us/img268/6152/309767.jpg |archive-date=17 July 2011|df=mdy-all|url-status=dead}}</ref>
* {{flag|Czech Republic}}: Bushmaster M4A3 B.M.A.S., Daniel Defense M4A1 and MK18 is used by (601st Special forces group, Military police, 43rd Airborne mechanized battalion) of [[Military of the Czech Republic|Czech Army]].<ref>{{cite book |url=http://www.army.cz/assets/files/9334/zbrane_definit.pdf |title=RUČNÍ ZBRANĚ AČR |archive-url=https://web.archive.org/web/20120229001255/http://www.army.cz/assets/files/9334/zbrane_definit.pdf |archive-date=2012-02-29 |publisher=Ministerstvo obrany České republiky AVIS|date=18 April 2007 |isbn=978-80-7278-388-5|language=cs}}</ref><ref>{{cite web |url=https://www.armadninoviny.cz/601-skss-kupuje-nove-utocne-pusky-ar-15.html |title=Nové útočné pušky pro české speciální síly }}</ref>
* {{flag|China}}: A variant is made by [[Norinco]] as the [[Norinco CQ]]. CQ-A carbine variant used by the [[Sichuan]] Police Department, [[Chongqing]] [[SWAT]] teams, and the [[Snow Leopard Commando Unit]].<ref>{{cite web|url=https://www.thefirearmblog.com/blog/2013/06/23/chinese-special-forces-competing-ar-15-rifles/|title=Chinese Special Forces Competing With AR-15 Rifles|website=TheFirearmBlog.com|date=23 June 2013 |access-date=29 December 2018|archive-url=https://web.archive.org/web/20181229171353/https://www.thefirearmblog.com/blog/2013/06/23/chinese-special-forces-competing-ar-15-rifles/|archive-date=29 December 2018|url-status=live}}</ref>
* {{flag|Colombia}}: M4A1s as part of a 2008 Foreign Military Sales.<ref name="Guns 2008">{{cite web|url=http://www.thegunzone.com/556dw-18.html |title=The 5.56 X 45mm: 2008 |publisher=The Gun Zone |access-date=2009-01-27 |author=Watters, Daniel |url-status=dead |archive-url=https://web.archive.org/web/20100104174625/http://thegunzone.com/556dw-18.html |archive-date=2010-01-04}}</ref> More M4/M4A1s announced to be sold via FMS program in 2017.<ref name="FB"/>
* {{flag|Costa Rica}}<ref name=colt_customers>{{cite web |url=http://www.colt.com/mil/customers.asp |title=Customers / Weapon users |website=Colt Defense Weapon Systems |archive-url=https://web.archive.org/web/20110902033712/http://www.colt.com/mil/customers.asp |archive-date=2 September 2011}}</ref>
* {{flag|Dominican Republic}}<ref>{{cite web|title=Soldiers from the Dominican Republic Special Forces fire the M4 Carbine rifle at targets down range at the shooting house in Sierra Piedras, Dominican Republic|date=20 April 2004|url=https://nara.getarchive.net/media/soldiers-from-the-dominican-republic-special-forces-fire-the-m4-carbine-rifle-caa11d|website=nara.getarchive.net|access-date=7 February 2019|archive-url=https://web.archive.org/web/20190209124518/https://nara.getarchive.net/media/soldiers-from-the-dominican-republic-special-forces-fire-the-m4-carbine-rifle-caa11d|archive-date=9 February 2019|url-status=live}}</ref>
* {{flag|East Timor}}<ref>{{cite web |title=VBSS Rehearsals |url=https://www.dvidshub.net/image/7641767/vbss-rehearsals |website=DVIDS |access-date=10 March 2023 |language=en}}</ref>
* {{flag|Ecuador}}: M4s sold as a 2008 Foreign Military Sales package.<ref name="Guns 2008"/>
* {{flag|Egypt}}<ref>{{cite web|url=https://sites.google.com/site/worldinventory/wiw_me_egypt|title=World Infantry Weapons: Egypt |website=World Inventory|access-date=2018-01-26|archive-url=https://web.archive.org/web/20160312102633/https://sites.google.com/site/worldinventory/wiw_me_egypt|archive-date=2016-03-12|url-status=dead}}</ref>
* {{flag|El Salvador}}: M4s sold as part of a 2007 Foreign Military Sales package.<ref name="Guns 2007">{{cite web|url=http://www.thegunzone.com/556dw-17.html |title=The 5.56 X 45mm: 2007 |access-date=2009-03-25 |author=Watters, Daniel |url-status=dead |archive-url=https://web.archive.org/web/20081010201552/http://www.thegunzone.com/556dw-17.html |archive-date=2008-10-10}}</ref> Additional M4s sold as a 2008 Foreign Military Sales package.<ref name="Guns 2008"/>
* {{flag|France}}: Used by the [[1st Marine Infantry Parachute Regiment|1er RPIMa]]{{Sfn|Rottman|2011|p=60}}
* {{flag|Georgia}}: [[Bushmaster M4-type Carbine|Bushmaster M4s]] being replaced by Colt M4s for the military. More M4/M4A1s announced to be sold via FMS program in 2017.<ref>{{cite web|url=https://special-ops.org/news/middle-east/colt-wins-multimillion-contract-sell-m4-carbines-georgia-iraq/|title=Colt wins multimillion contract to sell M4 Carbines to Georgia, Iraq|first=Eric|last=Sof|date=22 April 2017|access-date=2018-06-03|archive-url=https://web.archive.org/web/20180722130226/https://special-ops.org/news/middle-east/colt-wins-multimillion-contract-sell-m4-carbines-georgia-iraq/|archive-date=2018-07-22|url-status=dead}}</ref><ref name="FB"/> Joint Georgian-Israeli production M4 based "GI-4" launched in 2021<ref>{{cite web|url=https://rustavi2.ge/en/news/213295 |title=Georgia launches production of NATO standard GI-4 rifles |publisher=Rustavi2 |website=Rustavi2.ge |date=2021-10-28 |access-date=2022-02-10}}</ref>
* {{flag|Ghana}}<ref name="NMAA"/>
* {{flag|Greece}}: M16A2s and M4s are used by the "Special Forces" branch as well as by the airborne battalions of the Hellenic Army.{{citation needed|date=February 2024}}
* {{flag|Hungary}}: M4A1 SOPMOD by Hungarian MH 34th Bercsényi László special operation battalion<ref>{{cite web |url=http://shadowspear.com/hungary-special-operations/34-berceseny-laszlo-kulonleges-muveleti-zaszloalj.html |title=34. Bercsény László Különleges Műveleti Zászlóalj |trans-title=Bercsény László 34th Special Operations Battalion |access-date=June 22, 2017}}{{dead link|date=April 2025|bot=medic}}{{cbignore|bot=medic}}</ref> More M4/M4A1s announced to be sold via FMS program in 2017.<ref name="FB"/>
* {{flag|India}}: M4A1s as part of a 2008 Foreign Military Sales.<ref name="Guns 2008"/> M4A1 is used by the [[Mizoram Armed Police]], [[Parachute Regiment (India)|PARA SF]] and [[Force One (Mumbai Police)|Force One]] of the [[Mumbai Police]].<ref>{{cite web |url=http://www.meghalayatimes.info/index.php?option=com_content&view=article&id=13416:mizo-cops-to-get-foreign-weapons&catid=36:state&Itemid=29|title=Mizo cops to get foreign weapons|archive-url=https://web.archive.org/web/20111009063601/http://www.meghalayatimes.info/index.php?option=com_content&view=article&id=13416:mizo-cops-to-get-foreign-weapons&catid=36:state&Itemid=29 |archive-date=9 October 2011 |website=Meghalaya Times |date=2010-06-13 |access-date=2011-09-27 |df=mdy-all}}</ref><ref>{{cite web |title=Mizoram Armed Police |url=http://www.hindu.com/2009/04/08/stories/2009040861831000.html |work=[[The Hindu]] |date=2009-04-08 |access-date=April 8, 2011}} {{dead link|date=April 2021|bot=medic}}{{cbignore|bot=medic}}</ref>
* {{flag|Indonesia}}: Used by [[Detachment 88|Detachment 88 Counter-terrorism Police Squad]] operators.<ref>{{cite web |url=http://www.atimes.com/atimes/Southeast_Asia/IF16Ae01.html |title=Another success for Detachment 88 |author=Guerin, Bill |publisher=Asia Times Online |access-date=2009-01-20 |date=2007-06-16 |archive-url=https://web.archive.org/web/20090202151451/http://www.atimes.com/atimes/Southeast_Asia/IF16Ae01.html |archive-date=2009-02-02 |url-status=unfit|df=mdy-all}}</ref> Also used by ''[[Kopaska|Komando Pasukan Katak]]'' (Kopaska) tactical diver group and ''[[Kopassus|Komando Pasukan Khusus]]'' (Kopassus) special forces group.<ref name="idnvojnik">{{cite web|url=http://www.hrvatski-vojnik.hr/hrvatski-vojnik/1612007/ind.asp |title=Kopassus & Kopaska – Specijalne Postrojbe Republike Indonezije |trans-title=Kopassus & Kopaska - Special Forces of the Republic of Indonesia|language=hr |publisher=Hrvatski Vojnik Magazine |access-date=2010-06-12 |url-status=dead |archive-url=https://web.archive.org/web/20100822145526/http://www.hrvatski-vojnik.hr/hrvatski-vojnik/1612007/ind.asp |archive-date=August 22, 2010}}</ref>
* {{flag|Iraq}}: Used by the [[Iraqi Army]].<ref>{{cite web |url=http://www.stripes.com/article.asp?section=104&article=53489&archive=true |title=Iraqi soldiers switching over to M-16s and M-4s |author=Giordono, Joseph |access-date=2009-03-25 |date=2007-05-16 |publisher=[[Stars and Stripes (newspaper)|Stars & Stripes]] |archive-url=https://web.archive.org/web/20090801215346/http://www.stripes.com/article.asp?section=104&article=53489&archive=true |archive-date=2009-08-01 |url-status=dead}}</ref> Main weapon of the [[Iraqi National Counter-Terrorism Force]].<ref>{{cite web |url=http://www.professionalsoldiers.com/files/tos_apr_06.pdf |title=U.S. Special Forces, Iraqi army ops: Raids result in 102 detainees, large weapons cache, no losses |access-date=2009-03-25 |author=CJSOTF-AP Public Affairs |page=8 |archive-url=https://web.archive.org/web/20090327062451/http://www.professionalsoldiers.com/files/tos_apr_06.pdf |archive-date=2009-03-27 |url-status=dead}}</ref> More M4/M4A1s announced to be sold via FMS program in 2017.<ref name="FB"/>
** {{flag|Kurdistan Region}}: Used by [[Peshmerga]].<ref>{{cite web |date=January 14, 2020 |title='Delta Defence Group' Part Two: The Rifle |url=https://silahreport.com/2020/01/14/delta-defence-group-part-two-the-rifle/ |access-date=7 January 2024 |website=silahreport.com}}</ref>
* {{flag|Israel}}: Sold as part of a January 2001 Foreign Military Sales package to Israel.<ref name="Guns_2000">{{cite web |url=http://www.thegunzone.com/556dw-12.html |title=The 5.56 X 45mm: 2000–2001 |author=Watters, Daniel |access-date=2009-03-25 |url-status=dead |archive-url=https://web.archive.org/web/20081010201403/http://www.thegunzone.com/556dw-12.html |archive-date=2008-10-10|df=mdy-all}}</ref> Standard issue in the [[Israel Defense Forces]], but it has been gradually replaced with the [[IWI Tavor]] since 2001.{{Sfn|McNab|2021|p=63-64}}
* {{flag|Italy}}: Special Forces<ref>{{cite web|url=http://www.colmoschin.it/page/carm4.asp |title=Armi > Fucili d'Assalto > Colt M4 |access-date=2010-07-18 |url-status=dead |archive-url=https://web.archive.org/web/20110722030839/http://www.colmoschin.it/page/carm4.asp |archive-date=2011-07-22 |language=it}} . colmoschin.it</ref>
* {{flag|Jamaica}}: M4s sold as part of a 2007 Foreign Military Sales package.<ref name="Guns 2007"/>
* {{flag|Japan}}: M4A1s as part of a 2008 Foreign Military Sales package.<ref name="Guns 2008"/> M4A1 SOPMOD rifles are in use by the [[Special Forces Group (Japan)|Japanese Special Forces Group]],<ref>{{cite web |url=http://spikemilrev.com/news/2008/7/29-3.html |script-title=ja:全文掲載：飯柴大尉の声明文 |access-date=2009-01-12 |language=ja |title=Tomoaki Ishiba's statement |archive-url=https://web.archive.org/web/20090202113424/http://spikemilrev.com/news/2008/7/29-3.html |archive-date=2009-02-02 |url-status=dead|df=dmy-all}}</ref> but is supposedly denied by the JGSDF after Ishiba was arrested for violating American export laws.<ref>{{cite web |url=http://jieitaisaiyou.web.fc2.com/tokusyu.html |title=陸上自衛隊特殊作戦群 &#124; 自衛隊採用ガイド |website=jieitaisaiyou.web.fc2.com |access-date=11 January 2022 |archive-url=https://web.archive.org/web/20160124170956/http://jieitaisaiyou.web.fc2.com/tokusyu.html |archive-date=24 January 2016 |url-status=dead}}</ref>
* {{flag|Jordan}}: M4s sold as part of a 2007 Foreign Military Sales package.<ref name="Guns 2007"/> Additional M4s sold as a 2008 Foreign Military Sales package.<ref name="Guns 2008"/> More M4/M4A1s announced to be sold via FMS program in 2017.<ref name="FB"/>
* {{flag|Kenya}}: Used by Kenyan troops [[Kenya Defence Forces]] in AMISOM ops.<ref name="NMAA">{{cite web|first1=Jeremy |last1=Binnie|first2=Erwan|last2= de Cherisey|archive-url=https://web.archive.org/web/20170622123315/http://www.janes.com/images/assets/520/71520/New-model_African_armies.pdf|title= New-model African armies|publisher= Jane's|date= 2017|archive-date= 22 June 2017|url=http://www.janes.com/images/assets/520/71520/New-model_African_armies.pdf}}</ref>
* {{flag|Kosovo}}<ref>US Directorate of Defense Trade Controls. Notifications to the 108th Congress (November 2009)</ref>
* {{flag|Kuwait}}<ref>US Directorate of Defense Trade Controls. Notifications to the 108th Congress (November 2004)</ref>
* {{flag|Lebanon}}: M4 components being sold to [[Lebanese Special Operations Command|Lebanese special forces]].<ref>{{cite web |url=http://www.disam.dsca.mil/pubs/Vol%2030_3/Castelli.pdf |title=Department of Defense to equip Lebanon's Special Forces with Small Arms, Vehicles |author=Christopher J. Castelli |access-date=2009-02-08 |date=September 2008 |publisher=DISAM Journal |archive-url=https://web.archive.org/web/20090327064024/http://www.disam.dsca.mil/pubs/Vol%2030_3/Castelli.pdf |archive-date=2009-03-27 |url-status=dead }}</ref> M4/M4A1s sold as a 2008 Foreign Military Sales package.<ref name="Guns 2008"/> More M4/M4A1s announced to be sold via FMS program in 2017.<ref name="FB"/>
* {{flag|Malaysia}}: Made under license by [[SME Ordnance]] Sdn Bhd.<ref name="Rifle"/> Used by military and police special forces.<ref>{{cite web |url=http://www.tactical-life.com/online/special-weapons/malaysian-special-forces |title=Malaysian Special Forces |author=Thompson, Leroy |date=December 2008 |publisher=Special Weapons |access-date=2009-12-17 |archive-url=https://web.archive.org/web/20091230203307/http://www.tactical-life.com/online/special-weapons/malaysian-special-forces/ |archive-date=2009-12-30 |url-status=dead}}</ref>
* {{flag|Morocco}}<ref>{{cite web |url=https://www.moroccoworldnews.com/2018/09/253860/moroccos-military-buys-us-m4-carbine-rifles-and-navy-systems |title=Morocco's Military Buys US M4 Carbine Rifles and Navy Systems |website=Morocco World News |author=Bazza, Tarek |date=2018-09-21 |access-date=29 December 2021}}</ref><ref>{{cite web |url=https://www.defenseworld.net/news/23384/Colt_to_Supply_10_000_M4 |title=Colt to Supply 10,000 M4, M4A1 Carbine Rifles to Pakistan, Afghanistan, Morocco |website=Defense World.net |author1= |date=2018-09-21 |access-date=29 December 2021|archive-url=https://web.archive.org/web/20211229171201/https://www.defenseworld.net/news/23384/Colt_to_Supply_10_000_M4#.YcyW-Z3P200| archive-date=2021-12-29}}</ref>
* {{flag|Nepal}}: 1,070 M4s,<ref>{{cite journal|title=Legacies of War in the Company of Peace: Firearms in Nepal|journal=Nepal Issue Brief|issue=2|date=May 2013|url=http://www.smallarmssurvey.org/fileadmin/docs/G-Issue-briefs/NAVA-IB2-Legacies-of-War.pdf|page=5|publisher=[[Small Arms Survey]]|access-date=2019-01-08|archive-url=https://web.archive.org/web/20140708052928/http://www.smallarmssurvey.org/fileadmin/docs/G-Issue-briefs/NAVA-IB2-Legacies-of-War.pdf|archive-date=2014-07-08|url-status=dead}}</ref> sold as part of a 2005 Foreign Military Sales package.<ref name="Colt"/>
* {{flag|New Zealand}}: Used by [[New Zealand Special Air Service|NZSAS operators]] and standard issue to [[New Zealand Police]] including [[Special Tactics Group]] and [[Armed Offenders Squad]] units.<ref>{{cite web |url=http://www.diggerhistory.info/pages-army-today/rar-sasr/nz-sas.htm |title=Unofficial New Zealand Special Air Service page |access-date=2009-03-25 |archive-url=https://web.archive.org/web/20041112140414/http://www.diggerhistory.info/pages-army-today/rar-sasr/nz-sas.htm |archive-date=2004-11-12 |url-status=live}}</ref><ref name="Stuff.co.nz_1387878">{{cite news |url=http://www.stuff.co.nz/national/1387878 |title=Split second decisions: police rules of engagement |date=1 February 2009 |work=[[The Sunday Star-Times]] |access-date=15 October 2011 |archive-url=https://web.archive.org/web/20121012144700/http://www.stuff.co.nz/national/1387878 |archive-date=12 October 2012 |url-status=live}}</ref><ref>{{cite web|title=Replacement due for police rifles|url=http://www.police.govt.nz/news/release/1923|website=New Zealand Police|publisher=19 May 2005|access-date=8 March 2016|archive-url=https://web.archive.org/web/20160308212537/http://www.police.govt.nz/news/release/1923|archive-date=8 March 2016|url-status=live}}</ref>
* {{flag|North Macedonia}}: Used by the [[Army of North Macedonia]]<ref>{{cite web| url =https://www.janes.com/defence-news/news-detail/us-gifts-north-macedonia-colt-m4-rifles| title = US gifts North Macedonia Colt M4 rifles |date = 2021-03-03}}</ref>
* {{flag|Oman}}: M4/M4A1s announced to be sold via FMS program in 2017.<ref name="FB"/>
* {{flag|Pakistan}}: M4A1 variant used by the Special Forces of the Pakistani military besides the [[G3P4|POF G3P4]] standard rifle for the Pakistani military— also used by the [[Special Security Unit]] (SSU) of the [[Sindh Police]].<ref>{{cite web|title=Pakistan Army |url=http://www.defence.pk/pakistan-army/ |url-status=dead |archive-url=https://web.archive.org/web/20130513205333/http://www.defence.pk/pakistan-army/ |archive-date=May 13, 2013}}</ref><ref>{{cite web|url=https://fas.org/man/dod-101/sys/land/wsh2012/294.pdf|title=U.S. Army Weapon Systems Handbook 2012|access-date=2013-04-25|archive-url=https://web.archive.org/web/20171212062921/https://fas.org/man/dod-101/sys/land/wsh2012/294.pdf|archive-date=2017-12-12|url-status=live}}</ref> More M4/M4A1s announced to be sold via FMS program in 2017.<ref name="FB"/>
* {{flag|Palestinian Authority}}: Used by Palestinian security forces.<ref>{{cite web |author=Adnan Abu Amer |url=http://www.al-monitor.com/pulse/originals/2015/05/palestine-gaza-security-services-annual-budget-finance-aman.html |title=Security services drain Palestine's budget |publisher=Al-Monitor |date=2015-05-10 |access-date=2017-06-08 |url-status=dead |archive-url=https://web.archive.org/web/20170505024245/http://www.al-monitor.com/pulse/originals/2015/05/palestine-gaza-security-services-annual-budget-finance-aman.html |archive-date=2017-05-05}}</ref>{{Better source needed|reason=Not in article cited|date=November 2017}}
* {{flag|Panama}}: M4A1s sold as a 2008 Foreign Military Sales package.<ref name="Guns 2008"/> More M4/M4A1s announced to be sold via FMS program in 2017.<ref name="FB"/>
* {{flag|Peru}}: Airforce Special Group and anti-narcotics units<ref name=":1">{{Cite journal |issue=3 |volume=3 |title=Peruvian Small Arms: Gunning for the Shining Path |journal=Small Arms Defense Journal |url=https://sadefensejournal.com/peruvian-small-arms-gunning-for-the-shining-path/ |access-date=2022-10-26 |language=en-US}}</ref>
* {{flag|Philippines}}: Colt M4/M4A1s sold as a 2008 Foreign Military Sales package.<ref name="Guns 2008"/> 63,000 [[Remington R4|R4A3 rifles]] from [[Remington Arms]] for the [[Philippine Army]] and the [[Philippine Marine Corps]].<ref>{{cite web|url=http://www.janes.com/article/35909/philippine-army-acquires-r4-carbines |title=Philippine Army acquires R4 carbines |access-date=15 November 2014 |url-status=dead |archive-url=https://web.archive.org/web/20140329115549/http://www.janes.com/article/35909/philippine-army-acquires-r4-carbines |archive-date=March 29, 2014}}</ref><ref>{{cite web|url=http://www.interaksyon.com/article/60959/us-based-remington-wins-bid-to-supply-50000-m4-rifles-for-afp-company-rep-says|title=US-based Remington wins bid to supply 50,000 M4 rifles for AFP, company rep says|access-date=May 4, 2013|publisher=Interaksyon.com|url-status=dead|archive-url=https://web.archive.org/web/20130506172825/http://www.interaksyon.com/article/60959/us-based-remington-wins-bid-to-supply-50000-m4-rifles-for-afp-company-rep-says|archive-date=May 6, 2013}}</ref> Several units also used by the Defense Intelligence and Security Group.<ref name=Bullet-in201506>{{cite journal |date=June 2015 |title=Small Arms Repair and Upgrade Unit |journal=Bullet-in}}</ref>
* {{flag|Poland}}: Used by [[Polish Special Forces|Wojska Specjalne]] military unit [[GROM|JW Grom]].<ref>{{cite web |author=Sebastian Miernik |url=http://www.grom.mil.pl/uzbrojenie_pliki/UZBROJENIE.HTM |title=Uzbrojenie i wyposażenie |trans-title=Armaments and equipment|publisher=Grom.mil.pl |access-date=30 August 2010 |archive-url=https://web.archive.org/web/20110814155936/http://www.grom.mil.pl/uzbrojenie_pliki/UZBROJENIE.HTM |archive-date=14 August 2011|language=pl |url-status=dead}}</ref>
* {{flag|Romania}}: M4/M4A1s announced to be sold via FMS program in 2017.<ref name="FB"/>
* {{flag|Russia}}: Used in limited quantities by [[Alpha Group|FSB Alpha]]<ref>{{cite web|url=http://alldayplus.ru/society/7437-upravlenie-a-gruppa-alfa-i-ee-boevye-aksiomy-o-nashem-super-specpodrazdelenii.html|title=Спецподразделение "Группа "Альфа" ФСБ РФ. История, с иллюстрациями.|url-status=dead|archive-url=https://web.archive.org/web/20161210190121/http://alldayplus.ru/society/7437-upravlenie-a-gruppa-alfa-i-ee-boevye-aksiomy-o-nashem-super-specpodrazdelenii.html|archive-date=2016-12-10|language=ru}}</ref> and spotted in hands of [[Russian Armed Forces|RuAF]] in a training exercise.<ref>{{Cite web |date=2020-11-11 |title=FRIENDSHIP-2020 ~ Joint Russian-Pakistani SOF Exercise |url=https://www.joint-forces.com/special-forces/37530-friendship-2020-joint-russian-pakistani-sof-exercise |access-date=2024-01-30 |website=Joint Forces News|archive-url=https://web.archive.org/web/20240130175521/https://www.joint-forces.com/special-forces/37530-friendship-2020-joint-russian-pakistani-sof-exercise|archive-date= January 30, 2024|language=en-GB}}</ref>
* {{flag|Senegal}}: M4/M4A1s announced to be sold via FMS program in 2017.<ref name="FB"/> 2,200 M4s sold through FMS program in 2019.<ref>{{cite web |url=https://www.defenceweb.co.za/land/land-land/senegal-received-2-200-m4-carbines-from-the-us/ |title=Senegal received 2 200 M4 carbines from the US |date=26 July 2019 |website=defenceWeb}}</ref>
* {{flag|Serbia}}: Used by [[Gendarmery (Serbia)|Gendarmery]] and [[Special Anti-Terrorist Unit (Serbia)|Special Anti-Terrorist Unit]].<ref>{{cite web |url=http://www.kalibar.rs/code/navigate.php?Id=108&editionId=6&articleId=24 |title=Moderan "gradski" karabin |trans-title=A modern "city" carbine |publisher=Kalibar.rs |access-date=2010-08-30 |archive-url=https://web.archive.org/web/20120227190140/http://www.kalibar.rs/code/navigate.php?Id=108&editionId=6&articleId=24 |archive-date=2012-02-27 |url-status=live |language=sr}}</ref>
* {{flag|Singapore}}: Used by the [[Commandos (Singapore Army)|Commandos]] and the [[Police Coast Guard]] (only the Port Squadron and the Coastal Patrol Squadron) of the [[Singapore Police Force]].<ref>{{cite web|url=http://www.hrvatski-vojnik.hr/hrvatski-vojnik/2122008/singapur.asp |title=Singapurske Specijalne Postrojbe |trans-title=Singapore Special Forces|language=hr |publisher=Hrvatski Vojnik Magazine |access-date=2009-10-25 |url-status=dead |archive-url=https://web.archive.org/web/20091015052841/http://www.hrvatski-vojnik.hr/hrvatski-vojnik/2122008/singapur.asp |archive-date=October 15, 2009}}</ref>{{Sfn|McNab|2021|p=60}}
* {{flag|Slovakia}}: M4/M4A1s announced to be procured via FMS program in 2017.<ref name="FB"/>
* {{flag|Sweden}}: 15000 M4A1s purchased directly from US Army stocks in 2024 to act as interim service weapons while awaiting full delivery of the new [[Automatkarbin 24]]<ref>{{cite web |url=https://www.svt.se/nyheter/inrikes/forsvarets-nodlosning-akutkoper-15-000-automatvapen-fran-usa |title=Försvarets nödlösning: Akutköper 15 000 automatvapen från USA |trans-title=Military's emergency solution: order 15000 automatic weapons from USA |language=sv |website=svt.se |date=2024-12-10|access-date=2024-12-10}}</ref>
* {{flag|Taiwan}}: Used by [[Republic of China Army]] and [[National Police Agency (Republic of China)|National Police Agency]]<ref>{{cite web |url=http://www.ptpolice.gov.tw/_teams/mobile/CmsShow.aspx?Parm=200718112014797,2006112110379234,5 |title= 屏東縣警察局保安隊 裝備介紹 |trans-title=Equipment introduction |archive-url=https://web.archive.org/web/20080518081632/http://www.ptpolice.gov.tw/_teams/mobile/CmsShow.aspx?Parm=200718112014797%2C2006112110379234%2C5|language=zh |archive-date=2008-05-18 |website=Ptpolice.gov.tw |date=2007-01-29|access-date= 2011-09-27|url-status=dead}}</ref>
* {{flag|Thailand}}: M4A1s sold as part of a 2006 Foreign Military Sales package.<ref name="Guns 2006"/>
* {{flag|Tonga}}: M4/M4A1s sold as a 2008 Foreign Military Sales package.<ref name="Guns 2008"/>
* {{flag|Tunisia}}: Used by the Tunisian Army's Special Forces Group (GFS), 51st Infantry Navy Commandos Regiment, Presidential Guard and various [[Tunisian National Guard|National Guard]] and [[Ministry of the Interior (Tunisia)|Police]] special forces units.<ref>{{cite web |url=https://www.upi.com/Defense-News/2018/09/21/Colt-contracted-for-M4-M4A1-rifles-for-foreign-military-sales/2991537537084/ |title=Colt contracted for M4, M4A1 rifles for foreign military sales |language=en |publisher=UPI |access-date=2018-09-21 |archive-url=https://web.archive.org/web/20180921161854/https://www.upi.com/Defense-News/2018/09/21/Colt-contracted-for-M4-M4A1-rifles-for-foreign-military-sales/2991537537084/ |archive-date=2018-09-21 |url-status=live}}</ref> Used by the [[Unité Spéciale – Garde Nationale]].<ref>{{cite web|title=International Glocks: Fighting Terror in Tunisia|url=https://www.tactical-life.com/lifestyle/military-and-police/glocks-fighting-terror-in-tunisia/|website=Tactical Life|date=18 March 2016|access-date=17 February 2021|archive-date=12 April 2021|archive-url=https://web.archive.org/web/20210412180448/https://www.tactical-life.com/lifestyle/military-and-police/glocks-fighting-terror-in-tunisia/|url-status=dead}}</ref>
* {{flag|Turkey}}: Produced under license by [[Sarsılmaz|Sarsılmaz Firearms]].<ref name="Colt">{{cite web|url=http://www.thegunzone.com/556dw-15.html |title=The 5.56 X 45mm: 2005 |access-date=2010-03-10 |author=Watters, David |url-status=dead |archive-url=https://web.archive.org/web/20110807101157/http://www.thegunzone.com/556dw-15.html |archive-date=2011-08-07}}</ref> 
* {{flag|Uganda}}: Used by Ugandan troops in AMISOM ops.<ref name="NMAA"/>
* {{UKR}}<ref>{{cite tweet |last=Tracker|first=Ukraine Weapons |title=#Ukraine: Unpacking a pristine American M4A1 carbine by a Ukrainian soldier. Approximately 7000 small arms (including M4A1 rifles) were recently donated to Ukraine by the United States as military aid.|user=UAWeapons|number=1525446213289533440 |date=May 14, 2022 |archive-url=https://web.archive.org/web/20220531034133/https://twitter.com/UAWeapons/status/1525446213289533440|archive-date=2022-05-31|url-status=live|access-date=20 May 2022 |language=en}}</ref>
* {{flag|United Arab Emirates}}: Purchased 2,500 M4 carbines in 1993.<ref>{{cite web|url=http://www.thegunzone.com/556dw-10.html|title=The 5.56 X 45mm: 1990–1994|author=Watters, Daniel |access-date=2009-03-25|url-status=dead|archive-url=https://web.archive.org/web/20100104174808/http://thegunzone.com/556dw-10.html|archive-date=2010-01-04|df=mdy-all}}</ref>
* {{flag|United States}}<ref name="hogg2002">{{cite book |author1=Hogg, Ian|date=12 November 2002|title=Jane's Guns Recognition Guide |publisher=Collins Reference |edition=3rd |isbn=000712760X}}</ref>
* {{URY}}: Colt M4 and Bushmaster M4 carbines for Special Operation Group (Metropolitan Police)<ref name="hogg2002"/>
* {{flag|Yemen}}: M4s sold as part of a 2006 Foreign Military Sales package.<ref name="Guns 2006"/>

=== Former users ===
* {{Flag|Islamic Republic of Afghanistan}}: Used by [[Afghan National Army Commando Corps|Afghan National Army commandos]] during the [[Taliban insurgency]].<ref>{{cite web|author=Petty Officer First Class David Votroubek|date=July–August 2008|title=New Gear for Afghan Commandos|url=http://www.almc.army.mil/alog/issues/JulAug08/newgear_afghan.html|url-status=dead|archive-url=https://web.archive.org/web/20090801215341/http://www.almc.army.mil/alog/issues/JulAug08/newgear_afghan.html|archive-date=2009-08-01|access-date=2009-03-24|publisher=[[United States Army Logistics Management College]]}}</ref><ref>{{cite web|author=Soraya Sarhaddi Nelson|date=23 July 2007|title=New Afghan Commandos Take to the Frontlines|url=https://www.npr.org/templates/story/story.php?storyId=12127848|url-status=live|archive-url=https://web.archive.org/web/20090802014144/http://www.npr.org/templates/story/story.php?storyId=12127848|archive-date=2009-08-02|access-date=24 March 2009|publisher=[[National Public Radio]]}}</ref> M4s sold as part of a 2006 [[Foreign Military Sales]] package.<ref name="Guns 2006" /> Additional M4s sold as a 2008 Foreign Military Sales package.<ref name="Guns 2008" /> Captured stocks currently in use with the [[Afghanistan|Islamic Emirate of Afghanistan]].<!-- Please provide a verifiable source for additions to list above per [[WP:Verify]], [[WP:CITE]]. -->

==Conflicts==
===1990s===
*[[Colombian conflict]] (1964–present){{citation needed|date=January 2020}}
*[[Civil conflict in the Philippines]] (1969–present)
*[[Insurgency in Jammu and Kashmir]] (1989–present)<ref>{{cite web |last1=Noir |first1=War |title=#Jammu & #Kashmir: A member of "Kashmir Tigers" (KT) was reportedly killed by Indian Forces during the clashes in #Doda. |url=https://x.com/war_noir/status/1805919255394680854 |website=x.com |access-date=26 June 2024}}</ref> 
*[[Kosovo War]] (1998–1999), first US military usage of the M4 carbine

===2000s===
*[[War in Afghanistan (2001–2021)]]
*[[Internal conflict in Peru]]<ref name=":1" />
*[[Iraq War]] (2003–2011)
*[[South Thailand insurgency]] (2004–present)
*[[2006 Lebanon War]] (2006){{citation needed|date=January 2020}}
*[[Mexican drug war]] (2006–present){{citation needed|date=January 2020}}
*[[Russo-Georgian War]] (2008)<ref>{{cite web|date=2015-01-19|title=How Did American Weapons End Up at Donetsk Airport?|url=https://www.bellingcat.com/news/2015/01/19/how-did-american-weapons-end-up-at-donetsk-airport/|access-date=2021-01-14|website=bellingcat|language=en-GB}}</ref>
*[[Gaza War (2008–2009)]]
*[[Insurgency in Paraguay]]<ref>{{cite web|title=El atentado más cruel del EPP en 19 años - Notas - ABC Color|url=https://www.abc.com.py/edicion-impresa/notas/el-atentado-mas-cruel-del-epp-en-19-anos-1513026.html|access-date=2021-04-21|website=www.abc.com.py|language=es}}</ref>

===2010s===
*[[Syrian civil war]] (2011–2024)<ref name="militarytimes2">{{cite web|url=https://www.militarytimes.com/news/your-military/2017/05/07/syrian-kurds-are-now-armed-with-sensitive-us-weaponry-and-the-pentagon-denies-supplying-it/|title=Syrian Kurds are now armed with sensitive US weaponry, and the Pentagon denies supplying it|last=Snow|first=Shawn|language=en-us |publisher= [[Army Times|Military Times]]|date=2017-05-07|access-date=2019-04-22|archive-url=https://web.archive.org/web/20190422171028/https://www.militarytimes.com/news/your-military/2017/05/07/syrian-kurds-are-now-armed-with-sensitive-us-weaponry-and-the-pentagon-denies-supplying-it/|archive-date=2019-04-22|url-status=live}}</ref>
*[[2013 Lahad Datu standoff|Lahad Datu standoff (2013)]]<ref>{{cite web|url=http://www.sabahdaily.com/2013/02/gambar-penceroboh-di-lahad-datu-sabah.html|title=Intruders photo in Sabah|website=Sabah Daily|language=ms|access-date=2013-03-02|url-status=dead|archive-url=https://web.archive.org/web/20130306064532/http://www.sabahdaily.com/2013/02/gambar-penceroboh-di-lahad-datu-sabah.html|archive-date=2013-03-06|df=dmy-all}}</ref>
*[[War in Iraq (2013–2017)]]<ref name="militarytimes2"/>
*[[Battle of Arsal (2014)]]
*[[Yemeni civil war (2014–present)]]
*[[Battle of Marawi]] (2017)<ref>{{cite web|url=http://www.thefirearmblog.com/blog/2017/06/22/arming-maute-group-marawi-city/|title=Arming the Maute Group in Marawi City |website=The Firearm Blog|date=22 June 2017|access-date=23 November 2017|archive-url=https://web.archive.org/web/20171114000335/http://www.thefirearmblog.com/blog/2017/06/22/arming-maute-group-marawi-city/|archive-date=14 November 2017|url-status=live}}</ref>

===2020s===
*[[2021 Beirut clashes]] (2021)<ref>{{cite news |title=Photos: Clashes in Beirut near protest against blast probe judge |url=https://www.aljazeera.com/gallery/2021/10/14/photos-armed-clashes-erupts-in-beirut-in-protest-against-blast-judge |access-date=12 May 2022 |work= aljazeera.com |language=en}}</ref>
*[[Russian invasion of Ukraine]] (2022–present)<ref>{{cite tweet |last=Tracker |first=Ukraine Weapons |title=#Ukraine: A collection of a few of the weapons currently used by Ukrainian army: FN F2000 Tactical and M4A1 assault rifles + Beretta M9 and Glock 19 Gen 5, donated by allies.Classic Soviet Tokarev and Stechkin APS pistols + a modded AKS-74U are also seen. |user=UAWeapons |date=June 6, 2022 |number=1533911582639542273 |archive-url=https://web.archive.org/web/20220809205528/https://twitter.com/uaweapons/status/1533911582639542273 |archive-date=2022-08-09 |url-status=live |access-date=13 August 2022 |language=en}}</ref>
*[[Gaza war]] (2023–present)<ref>[https://www.indiatoday.in/world/story/israel-hamas-war-gaza-strip-us-made-weapons-found-with-terrorists-kashmir-afjanistan-taliban-2446590-2023-10-10 "From India to Israel, US weapons being used to attack its allies"]. indiatoday.in, 11 October 2023</ref>
*[[Ethnic violence in Papua New Guinea|2024 Enga Clashes]] (2024)<ref>{{Cite web |title=At least 64 killed in 'largest' tribal clashes in Papua New Guinea |url=https://www.aljazeera.com/news/2024/2/19/dozens-killed-in-largest-tribal-clashes-in-papua-new-guinea |access-date=2024-02-19 |website=Al Jazeera |language=en}}</ref>

==See also==
* [[Comparison of the AK-47 and M16]]
* [[AK-105]], a competing AK-74-based weapon
* [[SIG Sauer SIG516]], an M16-based rifle
* [[Bushmaster XM-15]]
* [[LWRC M6]], a competing M4-based weapon
* [[SIG Sauer SIGM400]]
* [[Adcor A-556|Brown Enhanced Automatic Rifle]], a competing M16/M4-based weapon
* [[LVOA]], a competing M4-based weapon
* [[Remington R4]], a competing M4-based weapon
* [[M231 Firing Port Weapon]]
* [[M16_rifle#M5 carbine|M5 Carbine]]
* [[LWRC M6]]
* [[Barrett M468]]

==References==
===Notes===
{{Notelist}}

===Citations===
{{Reflist|30em}}

=== Bibliography ===
* {{cite book |last1=Hogg |first1=Ian |author-link=Ian V. Hogg |last2=Weeks |first2=John |year=2000 |title=Military Small Arms Of The 20th Century |edition= 7th |publisher= KP Books |isbn=978-0873418249}}
*{{cite book |last=McNab |first=Chris |year=2021 |title=The M4 Carbine |series= |volume=Weapon 77 |publisher=[[Osprey Publishing]] |isbn=978-1472842275}}
*{{cite book |last=Rottman |first=Gordon |author-link=Gordon L. Rottman |year=2011 |title=The M16 |volume=Weapon 14 |publisher=Osprey Publishing |isbn=978-1-84908-691-2}}

==External links==
{{Commons category}}
* [http://www.colt.com/Catalog/LawEnforcement/Products/ColtLawEnforcementCarbine.aspx Colt M4's Law Enforcement page] {{Webarchive|url=https://web.archive.org/web/20160313091316/http://www.colt.com/catalog/lawenforcement/products/coltlawenforcementcarbine.aspx |date=13 March 2016 }} and [http://www.colt.com/Catalog/Military/Products/ColtM4Carbine.aspx Colt M4's Military page] {{Webarchive|url=https://web.archive.org/web/20140921011638/http://www.colt.com/Catalog/Military/Products/ColtM4Carbine.aspx |date=21 September 2014 }}
* [https://fnamerica.com/products/rifles/fn-m4a1/ FN M4A1 website]
* [http://www.military.com/NewsContent/0,13319,131317,00.html?wh=wh U.S. Army Won't Field Rifle Deemed Superior to M4] {{Webarchive|url=https://web.archive.org/web/20071011175138/http://www.military.com/NewsContent/0,13319,131317,00.html?wh=wh |date=2007-10-11 }}
* [http://www.armystudyguide.com/content/army_board_study_guide_topics/m4/m4-study-guide.shtml Online Army Study Guide] {{Webarchive|url=https://web.archive.org/web/20160304121056/http://www.armystudyguide.com/content/army_board_study_guide_topics/m4/m4-study-guide.shtml |date=2016-03-04 }}

{{ModernUSInfWeaponsNav}}
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[[Category:5.56×45mm NATO assault rifles]]
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[[Category:Carbines]]
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