M61 Vulcan

It is also manufactured under license in Japan by Sumitomo Heavy Industries for Japan's Self-Defense Force and by SNT Dynamics in South Korea.

• Name — M61 Vulcan • Origin — United States • Type — Rotary cannon • Is Ranged — yes • Service — 1959–present • Used By — United States, some NATO members, Japan, South Korea, Saudi Arabia, and others • Wars — * Vietnam War • Iran–Iraq War • Gulf War • 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 • Designer — General Electric • Design Date — 1946 • Manufacturer — General Dynamics Sumitomo Heavy Industries SNT Dynamics • Variants — See below • Weight — M61A2: (light barrel), (heavy barrel) • Cartridge — 20×102mm Vulcan • Caliber — 20 mm (0.8 in) • Barrels — 6-barrel (progressive RH parabolic twist, 9 grooves) • Action — Hydraulically operated, electrically fired, rotary cannon • Rate — 6,000 rounds per minute • Velocity — with PGU-28/B round • Range — About • Feed — Belt or linkless feed system

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-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 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. In 1947, the 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 with center line-mounted weapons could attack American aircraft from long range with their cannon main armament. American fighters with.50 caliber (12.7 mm) main armament, such as the P-51 and P-47, had to be close to enemy aircraft in order to cause significant damage to strong parts deep inside the jet. The Hispano cannon carried by the P-38 and P-61, while formidable against propeller-driven planes, had a relatively low rate of fire in the age of jets, while other Allied 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. 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 had done just that with a patent he filed in 1893. 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). Although European designers were moving towards heavier weapons for better hitting power, the U.S. initially concentrated on a powerful 0.60 in caliber 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. The first GE prototypes of the 0.60 in caliber T45 were ground-fired in 1949; it achieved 2,500 rpm, which was increased to 4,000 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 alternatives based on the 0.60 in 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 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. The development of the Lockheed F-104 Starfighter revealed that the T171 Vulcan (later redesignated M61) suffered problems with its 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. 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, 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.

Until the late 1980s, the M61 primarily used the M50 series of ammunition, which includes armor-piercing incendiary, high-explosive incendiary, and training rounds. The gun typically fires a 3.5 oz projectile at a muzzle velocity of about 3380 ft/s. A new PGU-28/B round was developed in the mid-1980s: a semi-armor-piercing high-explosive incendiary (SAPHEI) round, providing improvements in range, accuracy, and power over the preceding M56A3 HEI round. 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 3450 ft/s. 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. Due to safety issues, it was limited to emergency wartime use in 2000. Practically no powered rotary cannon is supplied with sufficient ammunition for a full minute of firing, due to weight (at 6,000 rpm, the projectiles alone would represent a mass of about for one minute of firing; and by including the brass shell, filling and primer the weight is approximately double that at). In order to avoid using 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 from two or three up to 40 or 50 can be selected. The size of the airframe and available internal space limits the size of the ammunition drum and thus the ammunition capacity. When vehicle-mounted, the only limiting factor is the vehicle's safe carry weight, so commensurately larger ammo storage is available. The main types of combat rounds include: • Designation — Type — Projectile weight [grains] — Bursting charge [grains] — Muzzle velocity [m/s] — Description • M53 — API —? — incendiary — 1,030 — RHA penetration at 0 degree impact angle and range. • M56A3/A4 — HEI — HE and incendiary — 1,030 — Nose fuzed round, no tracer. effective radius to produce casualties to exposed personnel. Fragmentation hazard out to. RHA penetration at 0 degree obliquity at range. • PGU-28A/B — SAPHEI — 1,050 — 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.

• Illustration — M61A1 Vulcan firing test aboard an F-105 Thunderchief. The Vulcan was first used in aerial combat on 4 April 1965, when four North Vietnamese Vietnam People's Air Force (VPAF) MiG-17s) attacked a force of 10 North American F-100 Super Sabres (two of which were assigned weather reconnaissance duties) escorting 48 Vulcan-armed and "bomb-laden" 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 20 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. The first confirmed Vulcan gun kill occurred on 29 June 1966 when Major Fred Tracy, flying his F-105 with the 421st TFS, fired 200 rounds of 20 mm into a MiG-17 that had just fired a 23 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. 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. It was integrated into the newer 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). The next generation of fighters built post-Vietnam incorporated the M61 gun internally. Combat kills using the M61 Vulcan in the Vietnam War 1966–1972 • Date/year — Firing aircraft — M61 Vulcan variant — Aircraft downed — USAF unit/comments • 29 June 1966 — F-105D Thunderchief — M61A1 — MiG-17 — 421st Tactical Fighter Squadron • 18 August 1966 — F-105D — M61A1 — MiG-17 — 34th TFS • 21 September 1966 — F-105D — M61A1 — MiG-17 — 333rd TFS • 21 September 1966 — F-105D — M61A1 — MiG-17 — 421st TFS • 4 December 1966 — F-105D — M61A1 — MiG-17 — 469th TFS • 1967 — F-105D/F-105F — M61A1 — (5) MiG-17 — 333rd TFS • 1967 — F-105D — M61A1 — (8) MiG-17 — 354th TFS • 1967 — F-105D/F-105F — M61A1 — (4) MiG-17 — 357th TFS • 1967 — F-4C Phantom II — SUU-16 gunpod — (2) MiG-17 — 480th TFS • 13 May 1967 — F-105D — M61A1 — MiG-17 — 44th TFS • 3 June 1967 — F-105D — M61A1 — MiG-17 — 13th TFS: Captain Ralph Kuster • 23 August 1967 — F-105D — M61A1 — MiG-17 — 34th TFS • 24 October 1967 — F-4D — SUU-23 gunpod — MiG-21 — 433rd TFS • 1967 — F-4D — SUU-23 — (3) MiG-17 — 435th TFS • 3 January 1968 — F-4D — SUU-23 — MiG-17 — 433rd TFS; pilot, Major B J Bogoslofski, WSO, Captain Richard L Huskey • 14 February 1968 — F-4D — SUU-23 — MiG-17 — 555th TFS • 1972 — F-4E — M61A1 — (3) MiG-21 — 35th TFS; the F4E was the first Phantom II to enter the war with an internal Vulcan gun. • 2 June 1972 — F-4E — M61A1 — MiG-19 — 58th TFS; first kill at supersonic speed (Mach 1.2); Major Phil Handley/WSO 1LT J. J. Smallwood • 9 September 1972 — F-4E — M61A1 — MiG-21 — 555th TFS • 15 October 1972 — F-4E — M61A1 — MiG-21 — 307th TFS • Total MiG-17 — |32 • Total MiG-19 — 1 • Total MiG-21 — 6 • Total — 39 • Illustration — An M61 mounted on a US Army 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 gunships, and was used in the tail turrets of both the Convair B-58 Hustler and Boeing B-52H Stratofortress bombers. Japan's Mitsubishi F-1 carried one internally mounted JM61A1 Vulcan with 750 rounds. • Illustration — An F-22 firing its M61A2 rotary cannon Two gun pod versions, the SUU-16/A (also designated M12 by the US Army) and improved 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 aerodynamic drag at higher speeds, while speeds under 400 mph did not provide enough airflow for the maximum rate of fire. 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 pods ejected empty cases and unfired rounds rather than retaining them. Both pods contained 1,200 rounds of ammunition, with a loaded weight of 1615 and 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. A variant with much shorter barrels, designated the M195, was also developed for use on the M35 Armament Subsystem as used on the 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 M97 universal turret mounting the M197 cannon. The M61 is also the basis of the US Navy Mk 15 Phalanx close-in weapon system and the M163 VADS Vulcan Air Defense System, using the M168 variant. On 13 December 2024, the Ukrainian Air Force claimed an F-16 shot down six Russian cruise missiles in one sortie. Two were shot down with “medium-range missiles”, another two with “short-range missiles” and finally two with the M61 Vulcan 20 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". On 20 August 2026, a Romanian Air Force F-16 destroyed an explosive naval drone near the Neptun Deep offshore platform using the onboard cannon. The drone was confirmed to not be Ukrainian as in the past incidents and the incident was attributed to Russia.

• M61A1 • M61A2 – The M61A2 shares the same features as the M61A1 but is 20% lighter.