The M61 and its derivatives have been the principal cannon armament of United States military fixed-wing aircraft for over sixty years. The M61 was originally produced by General Electric. After several mergers and acquisitions, it is produced by General Dynamics as of [update]. The higher speeds of jet-powered 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 C 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 an extremely high rate of fire with exceptional reliability.
In , the Air Force became a separate branch of the military. The new Air Force made a request for a new aircraft gun. A lesson of World War II air combat was that German, Italian, and Japanese fighters could attack American aircraft from long range with their cannon main armament. American fighters with. The 20 mm 0. In response to this requirement, the Armament Division of General Electric 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 electric power to operate the gun, and electric operation was more reliable than gas-operated reloading.
With multiple barrels, the rate of fire per barrel could be lower than a single-barrel revolver cannon while providing a greater overall rate of fire. The idea of powering a Gatling gun from an external electric power source was not a novel idea at the end of World War II, as Richard Jordan Gatling himself had done just that with a patent he filed in During World War I , a similar barreled Fokker-Leimberger aircraft rotary machine gun, powered by either the aircraft engine or an electric motor, had been under development by the German Empire.
In , the Army issued General Electric a contract for "Project Vulcan", a six-barrel weapon capable of firing 7, rounds per minute rpm. By the early s, the USAF decided that high velocity alone might not be sufficient to ensure target destruction and tested 20 and 27 mm 0.
