A revolver cannon is a type of autocannon, commonly used as an aircraft gun. It uses a cylinder with multiple chambers, similar to those of a revolver handgun, to speed up the loading-firing-ejection cycle. Some examples are also power-driven, to further speed the loading process. Unlike a rotary cannon, a revolver cannon only has a single barrel, so its spun weight is lower. Automatic revolver cannons have been produced by many different manufacturers.
Modern Mauser BK-27 aircraft revolver cannon
MLG 27 remote controlled revolver cannon on board an Elbe class tender of the German Navy
Rheinmetall RMK30 (TechDemo 2008 exhibition)
An autocannon, automatic cannon or machine cannon is a fully automatic gun that is capable of rapid-firing large-caliber armour-piercing, explosive or incendiary shells, as opposed to the smaller-caliber kinetic projectiles (bullets) fired by a machine gun. Autocannons have a longer effective range and greater terminal performance than machine guns, due to the use of larger/heavier munitions, but are usually smaller than tank guns, howitzers, field guns, or other artillery. When used on its own, the word "autocannon" typically indicates a non-rotary weapon with a single barrel. When multiple rotating barrels are involved, such a weapon is referred to as a "rotary autocannon" or occasionally "rotary cannon", for short.
US M242 Bushmaster 25 mm autocannon mounted on an M2 Bradley armoured fighting vehicle
ZU-23-2, a twin barrel 23×152 mm anti-aircraft autocannon from the 1960s still in service with some former members of the Warsaw Pact
German BK 5 50 mm aircraft autocannon displayed in front of the Me 262A jet, a design once tested with it
XM307 25 mm caliber man portable Automatic Grenade Launcher, part of the cancelled OCSW program