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The Minigun is a multibarreled 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 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, the term 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.

Contents 1 History 1.1 1890s: Electric motor-driven Gatling gun 1.2 1960s: Vietnam war 1.3 Variants 1.4 Gun pods and mounts 1.5 Non-aircraft applications 2 See also 3 References 4 External links

The ancestor to the modern minigun was made in the 1860s. Richard J. Gatling replaced the hand cranked mechanism of a rifle-caliber Gatling gun with an electric motor, a relatively new invention at the time. Even after Gatling slowed down the mechanism, the new electric-powered Gatling gun had a theoretical rate of fire of 3,000 rounds per minute, roughly three times the rate of a typical modern, single-barreled machine gun. Gatling's electric-powered design received US Patent #502,185 on July 25, 1893. Despite Gatling's improvements, the Gatling gun fell into disuse after cheaper, lighter-weight, recoil and gas operated machine guns were invented.

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 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 6,000 rounds per minute without overheating. 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.

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.

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) transport helicopters - a replacement for the aforementioned UH-1 Iroquois. More rarely, the minigun was mounted on Vietnam-era tanks.

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
N/A	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 a 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

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-2B/A by the U.S. Air Force. A variant was further 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 on as defensive armament on a number of helicopters and surface ships.

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").

The GE 7.62x51 mm Minigun has been used in gun pod applications by the United States and with purpose-built mounting hardware used on the aforementioned fixed wing gunship aircraft. In fact, before the purpose-built mounts were created, those aircraft used mounts simply designed to hold the gun pods that had already been developed.

Main article: U.S. Aircraft Gun Pods

US Army Designation	US Air Force Designation	US Navy Designation	Description
XM18	SUU-11/A	N/A	Gun pod fitted with the GAU-2/A 7.62 mm machine gun
XM18E1/M18	SUU-11A/A	N/A	SUU-11/A variant; various improvements including additional auxiliary power and selectable fire-rate capability (2,000 or 4,000 RPM)
M18E1/A1	SUU-11B/A	N/A	SUU-11A/A variant; differences unknown
N/A	MXU-470/A	N/A	Emerson Electric module for mounting a GAU-2B/A minigun; used in AC-47, AC-119G/K, and C-130A/E/H aircraft
N/A	N/A	Mk 77 Mod 0	Machine gun mount for the GAU-2/Mk 25 Mod 0/GAU-17 series of machine guns; deck mount applications

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.

Main article: U.S. Helicopter Armament Subsystems

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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."

• GShG-7.62 machine gun
• M61 Vulcan
• XM214 Microgun
• M197 Gatling gun
• Phalanx CIWS

• http://users.bigpond.net.au/minigun/specs.htm - Specs on a variety of minigun models
• http://www.freepatentsonline.com/20060207418.html - 2005 patent on a minigun design
• http://www.fas.org/man/dod-101/sys/ac/equip/m134.htm - Exploded diagrams and specifications
• Information on the XM214 from: Gervasi, Tom. Arsenal of Democracy III: America’s War Machine. New York, NY: Grove Press, 1984
• http://www.armamentsales.com - DeGroat Tactical Armaments; new production M134
• http://www.dillonaero.com - Dillon Aero; new production M134
• http://www.garwoodindustries.com - Garwood Industries; new production M134

• Video showing a CG animation of the firing process of a minigun.