Helicopter Minigun in Action Firing and Shooting in a Training Video of Chopper Gunships and the M134 Gatling Gun. The Wikipedia article gives details about the M134 Minigun – "The M134 Minigun is a 7.62 mm, six-barrelled machine gun with a high rate of fire (2,000 to 6,000 rounds per minute). It features Gatling-style rotating barrels with an external power source, normally an electric motor. The "Mini" of the name is in comparison to designs that use a similar firing mechanism but larger shells, such as General Electric's earlier 20-millimeter M61 Vulcan, and "gun" for a caliber size smaller than that a cannon, typically 20 mm and higher… In the 1960s, the United States armed forces 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. 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 7.62×51 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. The gun was originally specified to fire at 6,000 rpm, but this was later lowered to 4,000 rpm. 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.)"