The Probert Encyclopaedia of Warfare

M61A1

The General Electric M61A1 (Vulcan) is an American 20 mm calibre six-barrel Gatling gun mounted on the M163 AFV, and fitted to various aircraft. It has a variable rate of fire up to 6600 rounds per minute and a muzzle velocity of 1036 meters-per-second and fires APT ammunition with armour penetration of 45 mm at 500 meters and 31 mm at 1000 meters.
Research M61A1