Rotary cannon

During World War I, Imperial Germany worked on the Fokker-Leimberger, an externally powered 12-barrel Gatling gun that could fire more than 7,200 7.92×57mm rounds per minute.

[4] After World War II, the U.S. Army Air Force determined that an automatic cannon of improved design with an extremely high rate of fire was required to achieve a sufficient number of large-caliber hits on fast-moving enemy jet aircraft.

A larger-caliber cannon shell was deemed desirable as it could contain more explosives—compared to .30 and .50 caliber ammunition previously used—and thus able to destroy aircraft with only a few hits on target.

However, autocannons suffered from a lower rate of fire than machine guns; a possible solution, the M39 revolver cannon, had problems with overheating and excessive barrel wear.

In June 1946, the General Electric Company was awarded a U.S. military defense contract to develop an aircraft gun with a high rate of fire which GE termed Project Vulcan.

While researching prior work, ordnance engineers recalled the experimental electrically driven Gatling weapons of the turn of the 20th century.

One of the main reasons for the resurgence of the electrically or hydraulically powered multiple-barrel design is the weapon's tolerance for continuously high rates of fire.

For example, 1000 rounds per minute of continuous fire from a conventional single-barreled weapon ordinarily results in rapid barrel heating followed by stoppages caused by overheating.

The design is also resistant to defective ammunition, which can cause normal machine guns to malfunction when a cartridge fails to load, fire, or eject from the weapon.

While electric motors were used to rotate the Vulcan barrels, a few examples of self-operated Gatling-derived weapons use the blow-forward, recoil or gas impulse from their ammunition.

During the Vietnam War, the 7.62 mm caliber M134 Minigun was originally created to arm rotary-wing aircraft, and could be fitted to various helicopters as either a crew-served or a remotely operated weapon.

The crew's ability to concentrate the Minigun's fire very tightly produces the appearance of the 'Red Tornado'[7] from the light of the tracers, as the gun platform circles a target at night.