||This article needs additional citations for verification. (August 2010)|
A revolver cannon is a type of autocannon commonly used as an aircraft gun. It uses a cylinder with multiple chambers, like 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, but this is by no means universal. A revolver cannon differs from a Gatling gun in having only a single barrel, so the spun weight is lower and lends itself to gas operation. Automatic revolver cannons have been produced by many different European manufacturers, whereas the United States and to some extent Russia, generally favor the Gatling gun.
The archetypal revolver cannon is the Mauser MK 213, from which almost all current weapons are derived. In the immediate post-war era, Mauser engineers spread out from Germany and developed similar weapons around the world; both the British and French made outright copies of the 30 mm versions of the MK 213 as the ADEN and DEFA, respectively, Switzerland produced the Oerlikon KCA, while the U.S. used the 20 mm version, re-chambered for a slightly longer 102 mm cartridge intermediate between the 213's 82 mm and Hispano-Suiza HS.404's 110 mm. A number of larger experimental weapons were also developed, like the 42 mm Oerlikon RK 421, but did not see service.
Several generations of the basic ADEN/DEFA weapons followed, remaining largely unchanged into the 1970s. At that point a new generation of weapons developed, either for the proposed NATO 25 mm standard, or based on the Mauser 27 mm round; the leading current example is arguably the Mauser BK-27. The Rheinmetall Millennium 35 mm Naval Gun System is the largest to see service. The French GIAT 30 is a newer generation power-driven revolver cannon, and the Rheinmetall RMK30 modifies the GIAT system further by venting the gas to the rear to eliminate recoil.
The Hotchkiss Revolving Cannon of the late 19th century was not a revolver cannon in the modern sense, being of a Gatling type. Arguably, a forerunner was the Puckle gun, which was a manual revolver cannon, as opposed to an automatic one.
Automatic revolver cannons generally have a lower maximum sustained rate of fire than Gatling guns, as all the rounds are fired through a single barrel, which suffers from much higher heating loads. Cannon-calibre Gatling guns have a rate of fire of up to 10,000 rounds per minute or less (Gryazev-Shipunov GSh-6-23), while revolver cannon typically have a rate of fire of up to 2,000 rounds per minute or less. On the other hand, revolver cannon generally have a high initial firing rate due to the lower moving mass involved – only the chambers are being spun. Gatling type guns spin the whole multiple barrel and breech assembly which in equal calibre versions can weigh hundreds of kilograms. Also, the external power source of US gatling guns provides less power in a burst than the gas-operation of a revolver cannon, so that about half a second of spin-up time is required until the maximum rate of fire is reached. As it avoids the additional weight of multiple barrels, a revolver cannon can fire a larger calibre projectile than a Gatling gun of the same weight.
See also 
- ShVAK cannon
- ShKAS machine gun
- Mauser MK 213
- MANTIS - The German Army's new very short range protection system
- Rheinmetall RMK30
- ADEN cannon
- DEFA cannon
- M39 cannon
- GIAT 30
Notes and references 
- Anthony Williams, "The Red Queen and the Vigilante"
- The British were developing a 42 mm revolver cannon in the 1950s before cancelling in favour of missiles