M134 Minigun The Minigun ( also known as the M134 , GAU - 17 / A , and Mk 25 Mod 0 ) is a 7 . 62 mm , multi - barrel heavy machine gun with a high rate of fire ( 2 , 000 to 6 , 000 rounds per minute ) , employing Gatling - style rotating barrels with an external power source . Used by about 20 countrys on aircraft and surface vehicles alike , the minigun is a versatile and battle proven weapon . History . 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 them to repel attackers hidden in the dense jungle foliage often led to barrels overheating or cartridge jams . USAF helicopter crewman in Vietnam firing a minigun in 1968 . In order to develop a weapon with a more reliable , higher rate of fire , General Dynamics designers scaled down the rotating - barrel 20 mm M61 Vulcan cannon for 7 . 62 x 51 mm NATO ammunition . The resulting weapon , designated M134 and known popularly as the Minigun , could fire up to 4 , 000 rounds per minute without overheating . ( Originally , the gun was specified 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 including the H - 53 ( MH - 53 Pave Low ) and the common H - 60 family ( UH - 60 Black Hawk , HH - 60 Pave Hawk , etc . ) . Several larger aircraft were outfitted with miniguns specifically for close air support : the A - 37 Dragonfly with an internal gun and with pods on wing hardpoints , and the A - 1 Skyraider also with pods on wing hardpoints . Other famous gunship airplanes were the AC - 47 Spooky , the AC - 119 gunship , and the AC - 130 gunship . Design . 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 . Variants . G . E . ' s minigun is in use in several branches of the US military , under a number of designations . The basic fixedarmament version was given the designation M134 by the U . S . Army , while exactly the same weapon was designated GAU - 2 / A by the U . S . Air Force . The USAF weapon has three subvariants , while the U . S . Army weapon appears to have incorporated many 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 " ) . Gun pods and other aircraft mounts . 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 War , remaining in inventory for a period afterward . The standard pod , designated SUU - 11 / A by the Air Force 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 20 mm cannon . 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 . Deception as an infantry weapon in media . It must be noted that the Minigun has been portrayed as a man portable infantry weapon in media . This in reality is impossible for a number of reasons ( IE : weight , ammo , recoil , power supply , field ruggedness etc . ) . There have been designs though but have never been accepted for use in this role . However , there are firearms that would fill the " Minigun " role for ground usage : the TKB - 059 and the AO - 63 assault rifle which fires up to 6000rpm bursts . Assault rifles , SMGs with more than one barrel , Or simply a GPMG with its ROF adjusted to rapid fire .