A rotary cannon, rotary autocannon, rotary gun or Gatling cannon, is any large-caliber multiple-barreled automatic firearm that uses a Gatling-type rotating barrel assembly to deliver a sustained saturational direct fire at much greater rates of fire than single-barreled autocannons of the same caliber. The loading, firing and ejection functions are performed simultaneously in different barrels as the whole assembly rotates, and the rotation also permits the barrels some time to cool. The rotating barrels on nearly all modern Gatling-type guns are powered by an external force such as an electric motor, although internally powered gas-operated versions have also been developed. The cyclic multi-barrel design synchronizes the firing/reloading sequence. Each barrel fires a single cartridge when it reaches a certain position in the rotation, after which the spent casing is ejected at a different position and then a new round is loaded at another position. During the cycle, the barrel has more time to dissipate some heat away to the surrounding air. Due to the usually cumbersome size and weight of rotary cannon, they are typically mounted on weapons platforms such as vehicles, aircraft, or ships, where they are often used in close-in weapon systems. History In 1852 a revolving barrel gun with a unique method of ignition was proposed by an Irish immigrant to America by the name of Delany. The Gatling gun was another gun to use rotating barrels. It was designed by the American inventor Dr. Richard J. Gatling in 1861 and patented in 1862. Hand cranked and hopper fed, it could fire at a rate of 200 rounds per minute. The Gatling gun was a field weapon, first used in warfare during the American Civil War and subsequently by European and Russian armies. The design was steadily improved; by 1876 the Gatling gun had a theoretical rate of fire of 1,200 rounds per minute, although 400 rounds per minute was more readily achievable in combat. By 1893, the M1893 Gatling gun could fire 800 to 900 rounds per minute. Ultimately the Gatling's weight and cumbersome artillery carriage hindered its ability to keep up with infantry forces over difficult ground and was superseded by lighter and more mobile machine guns such as the Maxim gun. All models of Gatling guns were declared obsolete by the U.S. Army in 1911, after 45 years of service. Development of modern Gatling-type guns After the Gatling gun was replaced in service by