View source for M61 Vulcan

{{Short description|20 mm Gatling-type rotary cannon}}
{{Use dmy dates|date=June 2022}}
{{Infobox weapon
|name= M61 Vulcan
|image= Vulcan1.jpg
|image_size= 300
|caption= An unmounted M61A1 Vulcan with [[flash suppressor]] used in the SUU-16/A gun pod
|origin= United States
|type= [[Rotary cannon]]
<!-- Type selection -->
|is_ranged= yes
<!-- Service history -->
|service= 1959–present
|used_by= United States, some [[NATO]] members, [[Japan]], [[South Korea]], [[Saudi Arabia]], and others
|wars= {{indented plainlist|
* [[Vietnam War]]
* [[Iran-Iraq war]]
* [[Gulf War]]
* [[War in Afghanistan (2001–2021)|War in Afghanistan]]
* [[Iraq War]]
* [[War in Iraq (2013–2017)]]
* [[Yemeni Civil War (2014–present)]]
* [[Saudi Arabian-led intervention in Yemen]]
* [[Turkish military operation in Idlib Governorate]]
* [[Russo-Ukrainian War]]
}}
<!-- Production history -->
|designer=[[General Electric]]
|design_date=1946
|manufacturer=[[General Dynamics]]<br/>[[Sumitomo Heavy Industries]]<br/>[[SNT Dynamics]]
|unit_cost=
|production_date=
|number=
|variants= See below
<!-- General specifications -->
|spec_label=
|weight= {{ubli|M61A1: {{cvt|248|lb|kg}}|M61A2: {{cvt|202|lb|kg}} (light barrel), {{cvt|228|lb|kg}} (heavy barrel)}}
|length= {{cvt|71.93|in|m|abbr=on}}
|part_length={{cvt|59.8|in|m|abbr=on}}
<!-- Ranged weapon specifications -->
<!-- Please fill in missing specifications if possible. -->
|cartridge=[[20×102mm Vulcan]]
|caliber= [[20 mm caliber|20 mm]] (0.787&nbsp;in)
|barrels= 6-barrel (progressive RH parabolic twist, 9 grooves)
|action= [[Hydraulic machinery|Hydraulically operated]], electrically fired, [[rotary cannon]]
|rate= 6,000 rounds per minute<ref>{{Cite web|url=https://www.gd-ots.com/armaments/aircraft-guns-gun-systems/m61a1/|title = » 20mm M61A1/M61A2 Gatling Gun}}</ref>
|velocity= {{cvt|3450|ft/s|m/s}} with PGU-28/B round
|range=About {{cvt|9842|ft|m|sigfig=1}}
|max_range=
|feed= Belt or linkless feed system
|sights=
}}

The '''M61 Vulcan''' is a [[Hydraulic machinery|hydraulically]], electrically, or [[pneumatics|pneumatically]] driven, six-[[Gun barrel|barrel]], air-cooled, electrically fired [[Gatling gun|Gatling-style]] [[rotary cannon]] which fires [[20 mm caliber|{{cvt|20 x 102|mm|in|3}}]] rounds at an extremely high rate (typically 6,000 rounds per minute). The M61 and its derivatives have been the principal cannon armament of [[United States Armed Forces|United States military]] [[fixed-wing aircraft]] for over sixty years.<ref name ="fas_m61"/>

The M61 was originally produced by [[General Electric]]. After several mergers and acquisitions, it is produced by [[General Dynamics]] {{as of|2000|lc=y}}.<ref name="fas_m61" /> It is also manufactured under license in Japan by [[Sumitomo Heavy Industries]] for Japan's [[Japan Self-Defense Force|Self-Defense Force]]<ref name= "sumitomo">{{cite web |url=https://www.mod.go.jp/asdf/airpark/GUIDE/equipment/weapon/m61.html |title=Air Self-Defense Force Aircraft Mounted Weapons |access-date= 2025-05-03 |publisher= [[Ministry of Defense (Japan)]] |archive-url= https://web.archive.org/web/20230304045206/https://www.mod.go.jp/asdf/airpark/GUIDE/equipment/weapon/m61.html |archive-date= 4 March 2023 |url-status= live }}</ref> and by [[SNT Dynamics]] in South Korea.<ref name="snt">{{cite web |url=http://www.hisntd.com/eng/business/fire.html |title=Gun & Artillery Systems|access-date= 2025-05-03 |publisher= [[SNT Dynamics]]}}</ref>

==Development==
At the end of [[World War II]], the [[United States Army Air Forces]] began to consider new directions for future [[military aircraft]] guns. The higher speeds of [[jet engine|jet-powered]] [[fighter aircraft]] meant that achieving an effective number of hits would be extremely difficult without a much higher volume of fire. While captured German designs (principally the [[Mauser MG 213|Mauser MG 213C]]) showed the potential of the single-barrel [[revolver cannon]], the practical rate of fire of such a design was still limited by ammunition feed and barrel wear concerns. The Army wanted something more advanced, combining an extremely high rate of fire with exceptional reliability.<ref name="archive.org">https://archive.org/stream/The_Machine_Gun_V5/The_Machine_Gun_V5_djvu.txt M61 Al, CHAG, and GAU-8/A Machine Guns, History of Vulcan</ref>

In 1947, the [[United States Air Force|Air Force]] became a separate branch of the military. The new Air Force made a request for a new aircraft gun. A lesson of World War II air combat was that German, Italian, and Japanese fighters could attack American aircraft from long range with their cannon main armament. American fighters with [[M2 Browning#AN.2FM2|.50&nbsp;caliber (12.7&nbsp;mm)]] main armament, such as the [[North American P-51 Mustang|P-51]] and [[Republic P-47 Thunderbolt|P-47]], had to be close to enemy aircraft in order to hit and damage them. The [[Hispano-Suiza HS.404|{{cvt|20|mm|in}} Hispano cannon]] carried by the [[Lockheed P-38 Lightning|P-38]] and [[Northrop P-61 Black Widow|P-61]], while formidable against propeller-driven planes, had a relatively low rate of fire in the age of jets, while other cannons were notoriously unreliable.

In response to this requirement, the Armament Division of General Electric resurrected an old idea: the multi-barrel [[Gatling gun]]. The original Gatling gun had fallen out of favor because of the need for an external power source to rotate the barrel assembly, but the new generation of turbojet-powered fighters offered sufficient [[electric power]] to operate the gun, and electric operation was more reliable than [[gas-operated reloading]].<ref name="img294.imageshack.us">{{Cite web |type= image |format= JPEG |place= US |publisher= Image shack |url= http://img294.imageshack.us/img294/2433/eleckeygatling.jpg |title= Elec key Gatling |access-date= 5 September 2010 |archive-url= https://web.archive.org/web/20110725152641/http://img294.imageshack.us/img294/2433/eleckeygatling.jpg |archive-date= 25 July 2011 |url-status=dead }}</ref>

With multiple barrels, the rate of fire per barrel could be lower than a single-barrel revolver cannon while providing a greater overall rate of fire. The idea of powering a Gatling gun from an external electric power source was not a novel idea at the end of World War II, as [[Richard Jordan Gatling]] himself had done just that with a patent he filed in 1893.<ref>[https://web.archive.org/web/20110725152641/http://img294.imageshack.us/img294/2433/eleckeygatling.jpg Archived copy of US Patent #502,185 by R.J. Gatling, for an electric-powered Gatling-gun]</ref>

During [[World War I]], a similar 12-barreled [[Fokker-Leimberger]] aircraft rotary machine gun, powered by either the aircraft engine or an electric motor, had been under development by the [[German Empire]].{{Citation needed|date=May 2023}}

In 1946, the Army issued General Electric a contract for "Project Vulcan", a six-barrel weapon capable of firing 7,200 rounds per minute (rpm).<ref>{{Cite web |title= The Gatling Gun |access-date=2008-09-28 |url= http://tri.army.mil/lc/cs/csa/aagatlin.htm#M61 |date=5 October 2005 |archive-url= https://web.archive.org/web/20080921095536/http://tri.army.mil/LC/CS/csa/aagatlin.htm |archive-date =2008-09-21 |publisher= Aircraft Armament & Small Arms Product Support Integration Directorate |first1= Paul F |last1= Wahl |first2= Donald R |last2= Toppel |orig-year= Arco Publishing Company, New York, NY, 1965}}</ref> Although European designers were moving towards heavier {{cvt|30|mm|in|3}} weapons for better hitting power, the U.S. initially concentrated on a powerful {{convert |0.60|in|mm|adj= on}} cartridge designed for a pre-war anti-tank rifle, expecting that the cartridge's high [[muzzle velocity]] would be beneficial for improving hit ratios on high-speed targets.<ref name="archive.org"/> The first GE prototypes of the {{convert|0.60|in|mm|adj=on}} caliber T45 were ground-fired in 1949; it achieved 2,500&nbsp;rpm, which was increased to 4,000&nbsp;rpm by 1950. Due to air combat experience in the [[Korean War]], the USAF decided that high velocity alone might not be sufficient to ensure target destruction and tested {{cvt|20|and|27|mm|in|sigfig=3}} alternatives based on the {{convert|0.60|in|mm|adj=on}} caliber cartridge. These variants of the T45 were known as the T171 and T150 respectively and were first tested in 1952. Eventually, the standard 20×102&nbsp;mm cartridge was determined to have the desired balance of projectile/explosive mass and muzzle velocity, resulting in an optimum balance of range, accuracy and kinetic energy on target.<ref>{{Cite web|url=https://www.dau.mil/cop/ammo/DAU%20Sponsored%20Documents/PEO%20Ammo%20Portfolio%20Book%202017.pdf|title=PEO Ammunition Systems|website=dau.mil|archive-url=https://web.archive.org/web/20181106171753/https://www.dau.mil/cop/ammo/DAU%20Sponsored%20Documents/PEO%20Ammo%20Portfolio%20Book%202017.pdf|archive-date=6 November 2018|url-status=live}}</ref>

The development of the [[Lockheed F-104 Starfighter]] revealed that the T171 Vulcan (later redesignated ''M61'') suffered problems with its [[Belt (firearms)|linked ammunition]], being prone to misfeed and presenting a [[foreign object damage]] hazard with discarded links. A linkless ammunition feed system was developed for the upgraded ''M61A1'', which subsequently became the standard cannon armament of U.S. fighters.<ref name ="f_106_delta_dart_m61">{{cite web|url=https://www.f-106deltadart.com/weapons_20mm_cannon.htm|title=M61A1 GAU 4 20-MM Vulcan Cannon|access-date=12 July 2017|archive-url=https://web.archive.org/web/20161125131351/http://www.f-106deltadart.com/weapons_20mm_cannon.htm|archive-date=25 November 2016|url-status=live}}</ref>

In 1993, [[General Electric]] sold its aerospace division, including GE Armament Systems along with the design and production tooling for the M61 and GE's other rotary cannon, to [[Martin Marietta]]. After Martin's merger with [[Lockheed Corporation|Lockheed]], the rotary cannon became the responsibility of Lockheed Martin Armament Systems. Lockheed Martin Armament Systems was later acquired by [[General Dynamics]], which produces the M61 and its variants {{as of|2000|lc=y}}.<ref name= "fas_m61">{{cite web |url= http://www.fas.org/man/dod-101/sys/ac/equip/m61.htm |title= M61 20mm cannon |access-date= 2009-02-28 |date= 23 April 2000 |publisher= [[Federation of American Scientists]] |archive-url= https://web.archive.org/web/20011214122616/http://www.fas.org/man/dod-101/sys/ac/equip/m61.htm |archive-date= 14 December 2001 |url-status= live }}</ref>

==Description==
[[File:M-61 Vulcan-28.jpg|thumb|right|An M61 Vulcan and the feed system for an [[McDonnell Douglas F/A-18 Hornet|F/A-18]], on a stand]]

Each of the cannon's six barrels fires once in turn during each revolution of the barrel cluster. The multiple barrels provide both a very high rate of fire—around 100 rounds per second—and contribute to prolonged weapon life by minimizing barrel erosion and heat generation.<ref>{{Cite book |last=Tucker |first=Spencer C. |url=https://books.google.com/books?id=-oaMBAAAQBAJ&dq=M61+Vulcan++rate+of+fire+%E2%80%93+around+100+rounds+per+second&pg=PA271 |title=Persian Gulf War Encyclopedia: A Political, Social, and Military History: A Political, Social, and Military History |date=2014-08-20 |publisher=ABC-CLIO |isbn=978-1-61069-416-2 |language=en}}</ref> The average time between jams or failures is in excess of 10,000 rounds, making it an extremely reliable weapon.<ref>{{Cite web |date=2023-01-31 |title=U.S. Hypersonic Weapons and Alternatives {{!}} Congressional Budget Office |url=https://www.cbo.gov/publication/58924 |access-date=2023-06-24 |website=www.cbo.gov |language=en}}</ref> The success of the Vulcan Project and its progeny, the very-high-speed Gatling gun, has led to guns of the same configuration being referred to as [[wikt:Vulcan cannon|"Vulcan cannons"]], which can sometimes confuse nomenclature on the subject.

Most aircraft versions of the M61 are hydraulically driven and electrically primed. The gun rotor, barrel assembly and ammunition feed system are rotated by a hydraulic drive motor through a system of flexible drive shafts. The round is fired by an electric priming system where an electric current from a firing lead passes through the firing pin to the primer as each round is rotated into the firing position.<ref name="Air Force Manual 11W1-12-4-32">Air Force Manual 11W1-12-4-32</ref>

[[File:F-104 Waffenschacht.jpg|thumb|left|Gun installation on West German [[F-104]].]]
The self-powered version, the GAU-4 (called M130 in Army service), is [[gas-operated]], tapping gun gas from three of the six barrels to operate the gun gas-driven mechanism. The self-powered Vulcan weighs about {{convert|10|lb|kg|order=flip}} more than its electric counterpart, but requires no external power source to operate, except for an electric inertia starter to initiate gun rotation, allowing the first rounds to be chambered and fired.<ref name="Air Force Manual 11W1-12-4-32"/>

The initial M61 used linked ammunition, but the ejection of spent links created considerable (and ultimately insuperable) problems. The original weapon was soon replaced by the M61A1, with a linkless feed system. Depending on the application, the feed system can be either single-ended (ejecting spent cases and unfired rounds) or double-ended (returning casings back to the magazine). A disadvantage of the M61 is that the bulk of the weapon, its feed system, and ammunition drum make it difficult to fit it into a densely packed airframe.<ref>{{Cite web|url=http://archive.org/details/The_Machine_Gun_V5|title=The Machine Gun V5|via=Internet Archive}}</ref>

[[File:Tactical Weapons Effects Tests U.S. Air Force F-100, F-104, F-105 Aircraft.webm|thumb|De-classified Tactical Weapons Effects Tests of the U.S. Air-Force Century-Series aircraft.]]
The feed system must be custom-designed for each application, adding {{cvt|300|to|400|lb|kg|order=flip}} to the complete weapon. Most aircraft installations are double-ended, because the ejection of empty cartridges can cause a foreign-object damage hazard for jet engines and because the retention of spent cases assists in maintaining the center of gravity of the aircraft.<ref>{{Cite web |title=General Dynamics-OTS to supply M61A1 Vulcan 20mm guns for F-16s through FMS |url=https://airrecognition.com/index.php/news/defense-aviation-news/2021/december/7970-general-dynamics-ots-to-supply-m61a1-vulcan-20mm-guns-for-f-16s-through-fms.html |access-date=2023-06-24 |website=airrecognition.com}}</ref> The first aircraft to carry the M61A1 was the C model of the [[F-104 Starfighter|F-104]], starting in 1959.<ref>{{Cite book |last=Bowman |first=Martin W. |url=https://books.google.com/books?id=OwY0EAAAQBAJ&dq=The+first+aircraft+to+carry+the+M61A1+was+the+C+model+of+the+F-104,&pg=PA152 |title=Lockheed F-104 Starfighter: A History |date=2017-11-30 |publisher=Pen and Sword Aviation |isbn=978-1-4738-6329-3 |language=en}}</ref>

A lighter version of the Vulcan developed for use on the [[F-22 Raptor]], designated M61A2, is mechanically the same as the M61A1, but with thinner barrels to reduce overall weight to {{convert |202|lb|kg|order=flip}}. The rotor and housing have also been modified to remove any piece of metal not absolutely needed for operation and replaces some metal components with lighter-weight materials. The [[F/A-18E/F Super Hornet]] also uses this version.<ref>{{Citation |contribution-url = http://www.airforce-technology.com/projects/fa18/ |title = Projects |contribution = F/A-18E/F Super Hornet Maritime Strike Attack Aircraft |quote = ...&nbsp;features new lightweight gun system is the General Dynamics M61A2, which has a switchable firing rate of 4,000 or 6,000 rounds per minute and a fully integrated linkless ammunition feed system}}</ref>

The Vulcan's rate of fire is typically 6,000 rounds per minute, although some versions (such as that of the [[AMX International AMX|AMX]] and the [[F-106 Delta Dart]]) are limited to a lower rate, and others ([[A-7 Corsair]], [[F-15 Eagle]]) have a selectable rate of fire of either 4,000 or 6,000&nbsp;rounds per minute. The M61A2's lighter barrels allow a somewhat higher rate of fire, up to 6,600&nbsp;rounds per minute.<ref>{{cite web|title=GAU-4 20mm Vulcan M61A1/M61A2 20mm Automatic Gun|url=https://fas.org/man/dod-101/sys/ac/equip/m61.htm|publisher=Federation of American Scientists|access-date=4 January 2018|archive-url=https://web.archive.org/web/20170625123100/https://fas.org/man/dod-101/sys/ac/equip/m61.htm|archive-date=25 June 2017|url-status=live}}</ref>

<gallery mode="packed" heights="140">
File:M61 Vulcan.jpg|An M61 Vulcan at the [[Miramar Airshow]]
Image:AC-130A 20MM Vulcan Cannon Ammo belt.jpg|An M61 ammunition belt
File:M61A1-Vulcan--Independence-Day-2017-Tel-Nof-IZE-059.jpg|M61 on display
File:M61 Vulcan nose mounted 6-barreled Gatling cannon (11472816163).jpg|M61 Vulcan on display
File:PGU-27-AB-20-102mm-ammunition-m-61-vulcan.jpg|PGU-27 AB training rounds, Brussels 2015
</gallery>

===Ammunition===
Practically no powered rotary cannon is supplied with sufficient ammunition for a full minute of firing, due to its weight (at 6,000&nbsp;rpm, the projectiles alone would represent a mass of about {{cvt|600|kg}} for one minute of firing; and by including the brass shell, filling and primer the weight is slightly double that at {{cvt|1225|kg}}). In order to avoid using the 600 to 1,000 rounds carried by aircraft all at once, a burst controller is generally used to limit the number of rounds fired at each trigger pull. Bursts of from two or three up to 40 or 50 can be selected.<ref>{{Cite web |url=https://www.globalsecurity.org/military/systems/munitions/pgu-28.htm |title=Pgu-27A/B Tp/ Pgu-28A/B Saphei / Pgu-30A/B Tp-T |access-date=23 May 2019 |archive-url=https://web.archive.org/web/20190523213725/https://www.globalsecurity.org/military/systems/munitions/pgu-28.htm |archive-date=23 May 2019 |url-status=live }}</ref> The size of the airframe and available internal space limits the size of the ammunition drum and thus limits the ammunition capacity. When vehicle-mounted, the only limiting factor is the vehicle's safe carry weight, so commensurately larger ammo storage is available.

Until the late 1980s, the M61 primarily used the M50 series of ammunition in various types, typically firing a {{convert|3.5|oz|g|order=flip|adj=on}} projectile at a [[muzzle velocity]] of about {{convert|3380|ft/s|m/s|order=flip}}. A variety of armor-piercing incendiary (API), high-explosive incendiary (HEI), and training rounds are available.

A new PGU-28/B round was developed in the mid-1980s. It is a [[semi-armor-piercing high-explosive incendiary]] (SAPHEI) round, providing improvements in range, accuracy, and power over the preceding M56A3 HEI round.<ref name= GSPGU>{{Cite web |title=PGU-27A/B TP/PGU-28A/B SAPHEI/ GU-30A/B TP-T |url=http://www.globalsecurity.org/military/systems/munitions/pgu-28.htm |publisher=GlobalSecurity.org |access-date=2008-09-28 |archive-url=https://web.archive.org/web/20080916214052/http://www.globalsecurity.org/military/systems/munitions/pgu-28.htm |archive-date=16 September 2008 |url-status=live }}</ref> The PGU-28/B is a "low-drag" round designed to reduce in-flight drag and deceleration, and has a slightly increased muzzle velocity of {{convert |3450|ft/s|m/s|order=flip}}.<ref>{{cite web |title=20MM PGU-28 A/B |url=https://www.gd-ots.com/wp-content/uploads/2017/11/20mm-PGU-28-A-B-F-16.pdf |archive-url=https://web.archive.org/web/20190904002806/https://www.gd-ots.com/wp-content/uploads/2017/11/20mm-PGU-28-A-B-F-16.pdf |archive-date=2019-09-04 |url-status=live |publisher=General Dynamics Ordnance and Tactical Systems}}</ref> However, the PGU-28/B has not been without problems. A 2000 USAF safety report noted 24 premature detonation mishaps (causing serious damage in many cases) in 12 years with the SAPHEI round, compared to only two such mishaps in the entire recorded history of the M56 round. The report estimated that the PGU-28/B had a potential failure rate 80 times higher than USAF standards permit.<ref>{{Cite report |date=30 November 2001 |title=Ammunition Active |publisher= Airborne Weapons Corrective Action Program |url= https://tercel.mugu.navy.mil/drlog/awcap/volumes/vol8/ammo/v348_prob.pdf |url-status=dead |archive-date=17 October 2004 |archive-url = https://web.archive.org/web/20041017182625/https://tercel.mugu.navy.mil/drlog/awcap/volumes/vol8/ammo/v348_prob.pdf |id=14597 |section= PGU-28/B Premature Detonation in Barrel/Barrel Damage |pages= 1–6}}</ref> Due to safety issues, it was limited to emergency wartime use in 2000.<ref>''Jane's International Defense Review: IDR'', Volume 36, Issues 1–6. Jane's Information Group, 2003. "In 2000, the newer-technology PGU-28/B ammunition for the M61 was restricted to emergency wartime use after a series of mishaps."</ref>

The main types of combat rounds and their main characteristics are listed in the table:
{| class="wikitable" width="100%" style="text-align:center;"
|-
! Designation
! Type
! width=11%| Projectile weight [grains]
! width=11%| Bursting charge [grains]
! Muzzle velocity [m/s]
! Description
|-
| M53
| API
| ?
| {{cvt|65|gr|g oz}} incendiary<ref name="FM 1-140">{{citation |title=FM 1-140 Helicopter Gunnery |url=http://ugcsurvival.com/FieldManuals/FM%201-140%2019960329-Helicopter%20Gunnery.pdf |publisher=Department of the Army |year=1996}}</ref>
| 1,030
| align=left |{{cvt|0.25|in|mm|order=flip}} [[Rolled homogeneous armour|RHA]] penetration at 0&nbsp;degree impact angle and {{cvt|1000|m}} range.<ref name="FM 1-140"/>
|-
| M56A3/A4
| HEI
| {{cvt|1543|gr|g oz|1}}<ref name="FM 1-140"/>
| {{cvt|165|gr|g oz}} HE and {{cvt|20|gr|g oz}} incendiary<ref name="FM 1-140"/>
| 1,030
| align=left |Nose fuzed round, no tracer. {{cvt|2|m|ft}} effective radius to produce casualties to exposed personnel.<ref name="FM 1-140"/> Fragmentation hazard out to {{cvt|20|m|ft}}.<ref name="ORDATA" /> {{cvt|0.50|in|mm|1|order=flip}} RHA penetration at 0&nbsp;degree obliquity at {{cvt|104|m|ft}} range.<ref name="FM 1-140"/>
|-
| PGU-28A/B
| SAPHEI
| {{cvt|1580|gr|g oz|1}}<ref name= GSPGU/>
| {{cvt|10|g|gr oz|order=flip}}<ref name="ORDATA">{{cite web|title=ORDATA: Ordnance Identification Tool |publisher=JMU |url=http://maic.jmu.edu/ordata |url-status=dead |archive-url=https://web.archive.org/web/20080828231221/http://maic.jmu.edu/ordata/ |archive-date=28 August 2008 }}</ref>
| 1,050
| align=left |Multi-purpose fuzeless round with an incendiary charge in the nose setting off the HE behind it with a slight delay to maximize lethality against aircraft. No tracer or self-destruct. A [[zirconium]] pellet at the bottom of the HE cavity provides additional incendiary effect.
|}

==Applications and first combat use==
[[File:F105D M61.gif|thumb|M61A1 Vulcan firing test aboard an [[F-105 Thunderchief]].]]

The Vulcan was first used in aerial combat on 4 April 1965, when four [[North Vietnam]]ese [[Vietnam People's Air Force]] (VPAF) [[MiG-17]]s)<ref>Toperczer (MiG-17/MiG-19 Units) p. 65</ref> attacked a force of 10 [[North American F-100 Super Sabre]]s (two of which were assigned weather reconnaissance duties) escorting 48 Vulcan-armed and "bomb-laden" [[Republic F-105 Thunderchief|F-105 Thunderchiefs]], shooting down two of the latter. The MiG leader and only survivor from the four MiGs, Captain Tran Hanh, reported that U.S. jets had pursued them and that F-105s had shot down three of his aircraft, killing lieutenants Pham Giay, Le Minh Huan and Tran Nguyen Nam. Captain Donald Kilgus, piloting an F-100, received an official probable kill with his four [[M39 cannon|M39]] 20&nbsp;mm cannons during the engagement; however no other US pilot reported destroying any MiGs during the battle, leaving open the possibility that at least two of the MiG-17s may have been downed by their own [[anti-aircraft]] fire.<ref>Hobson p. 17</ref><ref>Anderton p. 71</ref><ref>Toperczer (MiG-17/MiG-19 Units) pp. 30, 31, 88</ref>

The first confirmed Vulcan gun kill occurred on 29 June 1966 when [[Major (rank)|Major]] Fred Tracy, flying his F-105 with the 421st TFS, fired 200 rounds of 20&nbsp;mm into a MiG-17 that had just fired a 23&nbsp;mm shell which entered one side of his cockpit and exited the other. When the VPAF MiG flew in front of him after making its pass, Tracy opened fire on it.<ref>McCarthy Jr. p. 38, photograph of 23&nbsp;mm cannon exit hole on Maj. Tracy's F-105</ref><ref>Michel III p. 56</ref>

The gun was installed in the Air Force's A-7D version of the [[LTV A-7 Corsair II]] where it replaced the earlier [[United States Navy]] A-7's [[Colt Mk 12 cannon]] and was adopted by the Navy on the A-7C and A-7E.<ref name = Chant1987>{{cite book|first= Christopher |last = Chant |title=A Compendium of Armaments and Military Hardware |url= https://books.google.com/books?id=k9cNAAAAQAAJ&pg=PA115 |year =1987|publisher=Routledge |isbn= 978-0-7102-0720-3 |pages = 65–70, 106, 114–15, 341–43, 363, 389, 404–5}}</ref> It was integrated into the newer [[McDonnell Douglas F-4 Phantom II|F-4E Phantom II]] variants. The F-4 was originally designed without a cannon as it was believed that missiles had made guns obsolete. Combat experience in Vietnam showed that a gun could be more effective than [[guided missiles]] in many combat situations and that an externally carried gun pod was less effective than an internal gun; the first generation of gun pods such as the SUU-16 were not oriented with the sights of the fighter. The improved pods were self-powered and properly synchronized to the sights, while the USAF versions of the F-4 were hastily fitted with internal M61 cannons in a prominent fairing under the nose, well before the war ended (Navy Phantoms never received cannons, continuing to rely on air-to-air missiles alone). [[Teen Series|The next generation]] of fighters built post-Vietnam incorporated the M61 gun internally.<ref>{{Cite web |url=https://www.af.mil/About-Us/Fact-Sheets/Display/Article/104505/f-16-fighting-falcon/ |title=F-16 Fighting Falcon |access-date=5 December 2018 |archive-url=https://web.archive.org/web/20181213203840/https://www.af.mil/About-Us/Fact-Sheets/Display/Article/104505/f-16-fighting-falcon/ |archive-date=13 December 2018 |url-status=live }}</ref><ref>{{Cite web |url=https://www.af.mil/About-Us/Fact-Sheets/Display/Article/104501/f-15-eagle/ |title=F-15 Eagle |work=Air Force |access-date=5 December 2018 |archive-url=https://web.archive.org/web/20181208140916/https://www.af.mil/About-Us/Fact-Sheets/Display/Article/104501/f-15-eagle/ |archive-date=8 December 2018 |url-status=live }}</ref><ref>{{Cite web |url=http://www.navalaviationmuseum.org/attractions/aircraft-exhibits/item/?item=f-14a_tomcat_flightline |title=F-14A Tomcat &#124; National Naval Aviation Museum |access-date=5 December 2018 |archive-url=https://web.archive.org/web/20181205145742/http://www.navalaviationmuseum.org/attractions/aircraft-exhibits/item/?item=f-14a_tomcat_flightline |archive-date=5 December 2018 |url-status=live }}</ref><ref>{{Cite web |url=https://www.boeing.com/history/products/fa-18-hornet.page |title=Boeing: Historical Snapshot: F/A-18 Hornet Fighter |access-date=5 December 2018 |archive-url=https://web.archive.org/web/20181205103355/https://www.boeing.com/history/products/fa-18-hornet.page |archive-date=5 December 2018 |url-status=live }}</ref>

{| class="wikitable"
|+ Combat kills using the M61 Vulcan in the Vietnam War 1966–1972<ref>McCarthy Jr. pp. 148–157. Excludes combination air-to-air missile/gun kills.</ref>
|-
! Date/year
! Firing aircraft
! M61 Vulcan variant
! colspan=2 | Aircraft downed
! USAF unit/comments
|-
|29 June 1966
|[[Republic F-105 Thunderchief|F-105D Thunderchief]]
|M61A1
| colspan=2 | [[MiG-17]]
|[[421st Tactical Fighter Squadron]]<ref>McCarthy Jr. p. 38</ref>
|-
|18 August 1966
|F-105D
|M61A1
| colspan=2 | MiG-17
|[[34th Fighter Squadron|34th TFS]]
|-
|21 September 1966
|F-105D
|M61A1
| colspan=2 | MiG-17
|[[333rd Fighter Squadron|333rd TFS]]
|-
|21 September 1966
|F-105D
|M61A1
| colspan=2 | MiG-17
|421st TFS
|-
|4 December 1966
|F-105D
|M61A1
| colspan=2 | MiG-17
|[[469th Flying Training Squadron|469th TFS]]
|-
|1967
|F-105D/F-105F
|M61A1
| colspan=2 | (5) MiG-17s
|333rd TFS
|-
|1967
|F-105D
|M61A1
| colspan=2 | (8) MiG-17s
|[[354th Fighter Squadron|354th TFS]]
|-
|1967
|F-105D/F-105F
|M61A1
| colspan=2 | (4) MiG-17s
|[[357th Fighter Squadron|357th TFS]]
|-
|1967
|[[McDonnell Douglas F-4 Phantom II|F-4C Phantom II]]
|[[SUU-16]] gunpod
| colspan=2 | (2) MiG-17s
|[[480th Fighter Squadron|480th TFS]]
|-
|13 May 1967
|F-105D
|M61A1
| colspan=2 | MiG-17
|[[44th Fighter Squadron|44th TFS]]
|-
|3 June 1967
|F-105D
|M61A1
| colspan=2 | MiG-17
|[[13th Fighter Squadron|13th TFS]]: Captain Ralph Kuster<ref>Campbell & Hill p. 43/photo of his F-105 plate # 213</ref>
|-
|23 August 1967
|F-105D
|M61A1
| colspan=2 | MiG-17
|34th TFS
|-
|24 October 1967
|F-4D
|[[SUU-23]] gunpod
| colspan=2 | [[MiG-21]]
|[[433rd Weapons Squadron|433rd TFS]]
|-
|1967
|F-4D
|SUU-23
| colspan=2 | (3) MiG-17s
|[[435th Fighter Training Squadron|435th TFS]]
|-
|3 January 1968
|F-4D
|SUU-23
| colspan=2 | MiG-17
|433rd TFS; pilot, Major B J Bogoslofski, [[Weapon systems officer|WSO]], Captain Richard L Huskey<ref>Davies, Osprey #45, p. 86</ref>
|-
|14 February 1968
|F-4D
|SUU-23
| colspan=2 | MiG-17
|[[555th Fighter Squadron|555th TFS]]
|-
|1972
|F-4E
|M61A1
| colspan=2 | (3) MiG-21s
|[[35th Fighter Squadron|35th TFS]]; the F4E was the first Phantom II to enter the war with an internal Vulcan gun.<ref>Michel III pp. 181, 267</ref>
|-
|2 June 1972
|F-4E
|M61A1
| colspan=2 | [[MiG-19]]
|[[58th Fighter Squadron|58th TFS]]; first kill at [[supersonic]] speed ([[mach number|Mach]]&nbsp;1.2); Major Phil Handley/WSO 1LT J. J. Smallwood<ref>Davies, Osprey #55, pp. 37–38</ref>
|-
|9 September 1972
|F-4E
|M61A1
| colspan=2 | MiG-21
|555th TFS
|-
|15 October 1972
|F-4E
|M61A1
| colspan=2 | MiG-21
|[[307th Fighter Squadron|307th TFS]]
|-
! colspan="6" |
|-
| colspan=3 |  
! Total MiG-17s
||32
|-
| colspan=3 |  
! Total MiG-19s
|1
|-
| colspan=3 |  
! Total MiG-21s
|6
|-
| colspan=3 |  
! Total
|39
|}

[[File:M163 VADS.JPEG|thumb|right|An M61 mounted on a US Army [[M163 VADS|M163]] armored vehicle.]]

The Vulcan was later fitted into the weapons bay of some [[Convair F-106 Delta Dart]] and [[General Dynamics F-111 Aardvark]] models. It was also adopted as standard in the "teen"-series air superiority fighters: the [[Grumman F-14 Tomcat]], the [[McDonnell Douglas F-15 Eagle]], [[General Dynamics F-16 Fighting Falcon]], and [[McDonnell Douglas F/A-18 Hornet]]. Other aircraft include the Italian/Brazilian [[AMX International AMX]] (on Italian aircraft only), and the [[F-22 Raptor]]. It was fitted in a side-firing installation on the [[Fairchild AC-119]] and some marks of the [[Lockheed AC-130]] [[gunship]]s, and was used in the tail turrets of both the [[Convair B-58 Hustler]] and [[Boeing B-52 Stratofortress|Boeing B-52H Stratofortress]] bombers.{{efn-lr|The B-52 Vulcans were removed in 1991.}} Japan's [[Mitsubishi F-1]] carried one internally mounted JM61A1 Vulcan with 750 rounds.<ref name=Chant1987 />

Two [[gun pod]] versions, the [[U.S. aircraft gun pods|SUU-16/A]] (also designated M12 by the US Army) and improved [[U.S. aircraft gun pods|SUU-23/A]] (US Army M25), were developed in the 1960s, often used on gunless versions of the F-4. The SUU-16/A uses the electric M61A1 with a [[ram-air turbine]] to power the motor. This proved to cause serious [[Drag (physics)|aerodynamic drag]] at higher speeds, while speeds under {{convert|400|mph|km/h|order=flip}} did not provide enough airflow for the maximum rate of fire.<ref>Gervasi, 1984. p. 239</ref>

The subsequent SUU-23/A uses the GAU-4/A self-powered Vulcan, with an electric inertia starter to bring it up to speed. Both [[gun pod|pods]] ejected empty cases and unfired rounds rather than retaining them. Both pods contained 1,200 rounds of ammunition, with a loaded weight of {{convert|1615|and|1720|lb|kg|order=flip}} respectively. During service in the [[Vietnam War]], the pods proved to be relatively inaccurate: the pylon mounting was not rigid enough to prevent deflection when firing, and repeated use would misalign the pod on its pylon, making matters worse.{{Citation needed |date = September 2014}}

A variant with much shorter barrels, designated the M195, was also developed for use on the [[U.S. Helicopter Armament Subsystems#AH-1 Cobra|M35 Armament Subsystem]] as used on the [[Bell AH-1 Cobra|AH-1G Cobra]] [[helicopter]]. This variant fed from ammunition boxes fitted to the landing skid and was developed to provide the AH-1 helicopter with a longer-range [[suppressive fire]] system before the adoption of the [[US Helicopter Armament Subsystems|M97 universal turret]] mounting the [[M197 Gatling gun|M197]] cannon.<ref>{{Cite web |url=https://centaursinvietnam.org/History/ihistoryEqOrd20mm.html |title=20mm Cannon |access-date=23 May 2019 |archive-url=https://web.archive.org/web/20190326104705/http://centaursinvietnam.org/History/ihistoryEqOrd20mm.html |archive-date=26 March 2019 |url-status=live }}</ref>

The M61 is also the basis of the US Navy [[Phalanx CIWS|Mk 15 Phalanx]] [[close-in weapon system]] and the [[M163 VADS]] Vulcan Air Defense System, using the M168 variant.<ref>{{Cite web |url=http://weaponsystems.net/weaponsystem/EE03%20-%20M163%20Vulcan.html |title=M163 Vulcan |access-date=23 May 2019 |archive-url=https://web.archive.org/web/20170112061408/http://www.weaponsystems.net/weaponsystem/EE03%20-%20M163%20Vulcan.html |archive-date=12 January 2017 |url-status=live }}</ref>

On 13 December 2024, the [[Ukrainian Air Force]] claimed an F-16 shot down 6 Russian cruise missiles. Two were shot down with “medium-range missiles”, another two with “short-range missiles” and finally two with the M61 Vulcan 20&nbsp;mm cannon. The pilot wasn't identified for security reasons but said: "A few bursts from the cannon — and an explosion... then another one! 'A secondary detonation,' I thought, but, as it turned out, there were two missiles," <ref>{{Cite news |date=2024-12-13 |title= In historic record, Ukrainian F-16 pilot downs 6 cruise missiles in single mission, Air Force claims |url= https://kyivindependent.com/ukrainian-f-16-pilot-downs-6-cruise-missiles/ |work=The Kyiv Independent| author= Martin Fornusek |language=en}}</ref>

==Variants==
* M61A1
* M61A2

==See also==
* [[GAU-12 Equalizer]] – General Electric, 25&nbsp;mm caliber
* [[GAU-13]] – General Electric, 30&nbsp;mm caliber
* [[GAU-19]] – General Electric, 12.7×99&nbsp;mm caliber
* [[GAU-22]] – General Dynamics, 25&nbsp;mm caliber, 4-barrel version of the GAU-12 mounted internally in the F-35A and in external gun pods on the F-35B and F-35C
* [[GAU-8 Avenger]] – General Electric, 30&nbsp;mm caliber
* [[M134 Minigun]] – 7.62&nbsp;mm cannon
* [[M163 VADS]] – self-propelled version of the M167 on an [[M113 armored personnel carrier]]
* [[M167 VADS]] – air defense system using the M61 Vulcan
* [[Machbet]] – Israeli upgrade of the M163 VADS incorporating the M61 Vulcan and four [[FIM-92 Stinger]] [[surface-to-air missile]] launch tubes
* [[XM301]] – cancelled lightweight 20&nbsp;mm cannon

'''Soviet Union/Russian Federation/CIS'''
* [[Gryazev-Shipunov GSh-6-23]] – 23&nbsp;mm caliber
* [[Gryazev-Shipunov GSh-30-1]] – 30&nbsp;mm caliber
* [[Gryazev-Shipunov GSh-6-30]] – 30&nbsp;mm caliber
* [[Gryazev-Shipunov GSh-30-2]] – 30&nbsp;mm caliber
* [[GShG-7.62 machine gun]] – 7.62&nbsp;mm caliber
* [[YakB-12.7 machine gun]] – 12.7&nbsp;mm caliber
* [[Shipunov 2A42]] – 30&nbsp;mm caliber autocannon

== Footnotes ==
{{Notelist-lr}}

==References==
{{reflist}}

==Bibliography==
* Anderton, David A. ''North American F-100 Super Sabre''. Osprey Publishing, 1987. {{ISBN|978-0-85045-662-2}}.
* Campbell, John M. and Hill, Michael. ''Roll Call: Thud: A Photographic Record of the F-105 Thunderchief''. 1996, Schiffer Publishing. {{ISBN|0-7643-0062-8}}.
* Davies, Peter E. ''U.S. Air Force F-4 Phantom II MiG Killers 1965–68''. Osprey Combat Aircraft #45, 2004, Osprey Publishing, UK. {{ISBN|1-84176-656-9}}.
* Davies, Peter E. ''USAF F-4 Phantom II MiG Killers 1972–73''. Osprey Combat Aircraft 55 (2005). {{ISBN|1-84176-657-7}}.
* Hobson, Chris. ''Vietnam Air Losses, United States Air Force, Navy and Marine Corps Fixed-Wing Aircraft Losses in Southeast Asia 1961–1973''. (2001) Midland Publishing. {{ISBN|1-85780-115-6}}.
* McCarthy, Donald J. Jr. ''MiG Killers, A Chronology of U.S. Air Victories in the Vietnam War 1965–1973''. Specialty Press; 2009 {{ISBN|978-1-58007-136-9}}.
* Michel III, Marshall L. ''Clashes, Air Combat Over North Vietnam 1965–1972''. Naval Institute Press; 1997. {{ISBN|978-1-59114-519-6}}.
* Toperczer, Istvan. ''MiG-17 and MiG-19 Units of the Vietnam War''. Osprey Combat Aircraft #25, 2008 2nd ed. {{ISBN|978-1-84176-162-6}}.

==External links==
{{commons}}
* {{cite web |url = http://tri.army.mil/lc/cs/csa/aagatlin.htm#M61 |title = Evolution of the M61 Vulcan Gatling Gun |publisher = Army |url-status = dead |archive-url = https://web.archive.org/web/20080921095536/http://tri.army.mil/LC/CS/csa/aagatlin.htm#M61 |archive-date = 21 September 2008 }}
* {{cite web |url = http://www.gd-ots.com/armament_systems/mbw_M61A1.html |publisher = General Dynamics Ordnance and Tactical Systems |title = M61A1/M61A2}}
* {{cite web |url = http://www.f-16.net/f-16_armament_article5.html |title = M61 A1 Vulcan – 20&nbsp;mm Gatling gun system |publisher = F-16}}
* {{cite web |url = http://www.fas.org/man/dod-101/sys/ac/equip/m61.htm |title = M61 $ |publisher = Federation of American Scientists}}

{{USAF weapons}}
{{Multiple Barrel Firearms}}
{{Modern Gatling Guns}}

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