202 pounds (92 kg) (excluding feed system) (M61A2)
(HEI) 100 g (3.5 oz) (projectile)
The M61 Vulcan is a hydraulically or pneumatically driven, six-barreled, air-cooled, electrically fired Gatling-style cannon, which fires 20 mm rounds at an extremely high rate. The M61 and its derivatives have been the principal cannon armament of United States military fixed-wing aircraft for fifty years. The M61 was originally produced by General Electric, and after several mergers and acquisitions is currently produced by General Dynamics.
During World War I, Germany was working on the Fokker-Leimberger, an externally-powered 12 barrel Gatling gun in the 7.92x57mm Mauser round capable of firing over 7,000 rpm, but its spent brass ruptured.
At the end of World War II, the United States Army began to consider new directions for future military aircraft guns. The higher speeds of jet-engined fighter aircraft meant that achieving an effective number of hits would be extremely difficult without a much higher volume of fire. While captured German designs (principally the Mauser MG 213C) showed the potential of the single-barrel revolver cannon, the practical rate of fire of such a design was still limited by ammunition feed and barrel wear concerns. The Army wanted something better, combining extremely high rate of fire with exceptional reliability.
In response to this requirement, General Electric Armament Division resurrected an old idea: the multi-barrel Gatling gun. The original Gatling gun had fallen out of favor because of the need for an external power source to rotate the barrel assembly, but the new generation of turbojet-powered fighters offered sufficient electrical power to operate the gun, and electric operation offered reliability superior to a gas operated weapon. With multiple barrels the rate of fire per barrel could be lower than a single-barrel revolver cannon while still giving a superior total rate of fire.
In and of itself, the idea of powering a Gatling gun from an external electric power source was not a novel idea at the end of the World War II era, as Richard Jordan Gatling himself did just that in 1893, in a patent he filed at that time.
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