Autocannon

An autocannon is a projectile weapon with a larger bore size than a machine gun, and a faster rate of fire than regular cannon used by artillery units. The term developed from WWII guns used in aircraft, where the distinction was that the bullets were explosive. After the war similar guns were used with non-explosive rounds in the anti-tank role, and the name autocannon started to become popular.

Examples of an autocannon would be the 25mm Bushmaster mounted on the AH-64 Apache and M2 Bradley, a Bofors 40mm anti-aircraft system or the 30mm GAU-8 from the A-10 Warthog close air support airframe. Several tank guns use auto loading systems, and could be considered autocannon even though they are large-bore (105 mm and more).