High Quality Content by WIKIPEDIA articles! The M134 Minigun is a 7.62 mm, six-barreled 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.