The minigun is a multi-barrel machine gun with a high rate of fire (several thousand rounds per minute), employing Gatling-style rotating barrels and an external power source. In popular culture, the term "minigun" has come to refer to any externally-powered Gatling gun of rifle caliber, though the term is sometimes used to refer to guns of similar rates of fire and configuration, regardless of power source and caliber. Specifically, minigun refers to a single weapon, originally produced by General Electric. The "mini" of the name is in comparison to designs that use a similar firing mechanism but 20 mm or larger shells, such as General Electric's earlier M61 Vulcan.
In the 1960s, the US military began exploring modern variants of the electric-powered, rotating barrel Gatling gun-style weapons for use in the Vietnam War. The US forces in Vietnam, which used helicopters as one of the primary means of transporting soldiers and equipment through the dense jungle, found that the thin-skinned helicopters were very vulnerable to small arms fire and rocket-propelled grenade (RPG) attacks when they slowed down to land. Although helicopters had mounted single-barrel machine guns, using single-barrel machine guns to repel attackers hidden in the dense jungle foliage often led to barrels overheating or cartridge jams.
In order to develop a weapon with a more reliable, higher rate of fire, General Electric designers scaled down the rotating-barrel 20 mm M61 Vulcan cannon for 7.62 x 51 mm NATO ammunition. The resulting weapon, designated XM134 and known popularly as the Minigun, could fire up to 4,000 rounds per minute without overheating. (Originally, the gun was specced at 6,000 rpm, but this was later lowered to 4,000.) The Minigun was mounted on OH-6 Cayuse and OH-58 Kiowa side pods, in the turret and wing pods on AH-1 Cobra attack helicopters, on door, pylon and pod mounts on UH-1 "Huey" Iroquois transport helicopters, and on many other helicopters and aircraft.
Several larger aircraft were outfitted with miniguns, specifically for close air support, including famous gunship airplanes like the Douglas AC-47 ("Spooky" a.k.a. "Puff the Magic Dragon", converted Douglas C-47s), AC-119 Gunship ("Shadow" and "Stinger", converted Fairchild "Flying Boxcars"), and the original AC-130 "Spectre" Gunship (converted C-130 Hercules cargo planes), the H-53 (MH-53 Pave Low), and the common H-60 family of helicopters (UH-60 Black Hawk/HH-60 Pave Hawk).
The basic weapon is a 6-barrel, air-cooled, and electrically driven machine gun. The electric drive rotates the weapon within its housing, with a rotating firing pin assembly and rotary chamber. The minigun's multibarrel design helps prevent overheating, but also serves other functions. Multiple barrels allow for a greater capacity for a high firing rate, since the serial process of firing/extraction/loading is taking place in all barrels simultaneously. Thus, as one barrel fires, two others are in different stages of shell extraction and another three are being loaded. The minigun is composed of multiple closed-bolt rifle barrels arranged in a circular housing. The barrels are rotated by an external power source: usually electric, pneumatic, or hydraulic. Other rotating-barrel cannons are powered by the gas pressure or recoil energy of fired cartridges. A gas-operated variant, designated the XM133, was also developed, but was not put into production.
While the weapon can feed from linked ammunition, it requires a delinking feeder to strip the links as the rounds are introduced to the chambers. The original unit was designated MAU-56/A, but has since been replaced by an improved MAU-201/A unit.
G.E.'s minigun is in use in all major branches of the US military, under a number of designations. The basic fixed armament version was given the designation M134 by the U.S. Army, while the exact same weapon was designated GAU-2/A by the U.S. Air Force. The USAF weapon has three subvariants, while the US Army weapon appears to have incorporated any new improvements without a change in designation. Available sources show a relation between both M134 and GAU-2/A and M134 and GAU-2B/A. A separate variant, designated XM196, with an added ejection sprocket was developed specifically for the XM53 Armament Subsystem on the AH-56 Cheyenne helicopter.
Another variant was developed by the U.S. Air Force specifically for flexible installations, at the time primarily for the UH-1N helicopter, as the GAU-17/A. The primary end users of the GAU-17/A have been the U.S. Navy and the U.S. Marine Corps, who mount them as defensive armament on a number of helicopters and surface ships. The weapon is part of both the A/A49E-11 armament system on the UH-1N and A/A49E-13 armament subsystem on the HH-60H aircraft. The weapons on these systems feature a selectable fire rate of either 2,000 or 4,000 rpm. There is mention of a possible GAUSE-17 designation (GAU-Shipboard Equipment-17), in reference to the system when mounted on surface ships, though this would not follow the official ASETDS designation system's format.
Other manufacturers in the United States also produce Miniguns with various refinements of their own, including Dillon Aerospace (the "M134D"), and Garwood Industries (the "M134G").
|US Army Designation||US Air Force Designation||US Navy Designation||Description|
|XM134/M134||GAU-2/A||N/A||7.62x51 mm NATO GE “Minigun” 6-barreled machine gun|
|N/A||GAU-2A/A||N/A||GAU-2/A variant; unknown differences|
|M134||GAU-2B/A||Mk 25 Mod 0||GAU-2A/A variant; unknown differences|
|N/A||GAU-17/A||N/A||GAU-2B/A variant; optimized for flexible use, uses either an MAU-201/A or MAU-56/A delinking feeder.|
|XM196||N/A||N/A||M134/GAU-2B/A variant; housing modified by addition of an ejection sprocket; for use in the XM53 armament subsystem on the AH-56 helicopter|
One of the first applications of the weapon was in aircraft armament pods. These gun pods were used by a wide variety of fixed and rotary wing aircraft mainly during the Vietnam conflict, remaining in inventory for a period afterward. The standard pod, designated SUU-11/A by the USAF and M18 by the US Army, was a relatively simple unit, completely self contained, with a 1,500 round magazine directly feeding delinked ammo into the weapon. This means the Minigun fitted to the pod does not require the standard MAU-56/A delinking feeder unit. A number of variations of this pod exist.
Initially on fixed-wing gunships, such as the AC-47 and AC-119 the side-firing armament was fitted by combining SUU-11/A aircraft pods, often with their aerodynamic front fairings removed, with a locally fabricated mount. These pods were essentially unmodified, required no external power, and were linked to the aircraft's fire controls. The need for those pods for other missions led to the development and fielding of a purpose built "Minigun module" for gunship use, designated the MXU-470/A. These units first arrived in January 1967 with features such as an improved 2,000 round drum and electric feeder allowing simplified reloading in flight. The initial units were unreliable and were withdrawn almost immediately. By the end of the year, however, the difficulties had been worked out and the units were again being fitted to AC-47s, AC-119s, AC-130s, and even being proposed for lighter aircraft such as the O-2 Skymaster. A fit of two MXU-470/As was also tested on the AU-23A Peacemaker, though the Royal Thai Air Force who later received these aircraft elected to use the other configuration utilizing the M197 20mm cannon.
|US Army Designation||US Air Force Designation||Description|
|XM18||SUU-11/A||Gun pod fitted with the GAU-2/A/M134 7.62 mm machine gun and fixed rate of fire of 4,000 RPM|
|XM18E1/M18||SUU-11A/A||SUU-11/A/XM18 variant; various improvements including additional auxiliary power and selectable fire-rate capability (2,000 or 4,000 RPM)|
|M18E1/A1||SUU-11B/A||SUU-11A/A/M18 variant; differences modified selectable fire-rate capability (3,000 or 6,000 RPM)|
|N/A||MXU-470/A||Emerson Electric module for mounting a GAU-2B/A minigun; used in AC-47, AC-119G/K, and AC-130A/E/H aircraft|
Various iterations of the minigun have also been used in a number of armament subsystems for helicopters, with most of these subsystems being created by the United States. The first systems utilized the weapon in a forward firing role, for a variety of helicopters, some of the most prominent examples being the M21 armament subsystem for the UH-1 Iroquois and the M27 for the OH-6 Cayuse. It also formed the primary turret mounted armament for a number of members of the AH-1 Cobra family. The weapon was also used as a pintle-mounted door gun on a wide variety of transport helicopters, a role it continues to serve in today.
While the minigun is primarily associated with fixed wing airplanes and helicopters it has occasionally been mounted on land vehicles. Since its creation, the US military have explored ways of using the weapon on vehicles and as a heavy infantry weapon, creating weapons such as the XM214. A pamphlet from the early sixties advertising the Cadillac Gage V100 (or XM706 as it was designated by the US Army) talks of "Firepower for Today's Army" showing a vehicle with the "XM-134/GAU-2B/A Minigun." The rate of fire is advertised as selectable from "500 to 6000 shots/minute."
|US Navy Designation||Description|
|Mk 77 Mod 0||Machine gun mount for the GAU-2/Mk 25 Mod 0/GAU-17 series of machine guns; deck mount applications|
The Minigun holds an almost iconic place in popular culture. Primarily a product of its inclusion as a personal weapon in the movies Predator (1987) and Terminator 2: Judgment Day (1991), the Minigun has been referenced in multiple genres spanning almost the entire gamut of media, from books and movies to anime and graphic novels to video and computer games. The visibility of the Minigun in media like the movie The Matrix (1999) has promoted its iconic position, as well as a fascination with the weapon among fans of associated media. In reality it is impossible to wield as an individual weapon and no Armed Forces do this in reality for many reasons, but this capability has been depicted in a wide variety of media.
The term "Minigun" itself has entered the lexicon as a term used to describe any machine gun with a rotary barrel arrangement, regardless of any relation to the original General Electric product. Technically speaking, however, the term "Minigun" only applies to the General Electric product family, with even other rifle caliber systems being referred to as Gatling-type rotary barrel machine guns. For instance, in Jane's Weapon Systems, 1986-1987, the 4-barrel rotary machine gun (unnamed at the time of the printing, the weapon is in fact the Yak-B 12.7mm machine gun) on the Mil Mi-24 is officially referred to as a "multi-barrelled, Gatling-type gun," while the General Electric weapon is referred to as a "Minigun". The term Chain gun has often become confused with Miniguns and other rotary barrel weapons in video games and other media.