   the m61 vulcan is a hydraulically or pneumatically driven, six-barrel, air-cooled, electrically fired gatling-style rotary cannon which fires 20&nbsp;mm rounds at an extremely high rate (typically 6,000 rounds per minute). 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. ==development== 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-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 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 1947, the air force became a separate branch of the military. the new air force made a request for a new aircraft gun. the lesson of wwii was that the german, italian and japanese fighters could reach out and touch the american fighters and bombers with their cannon main armament, while the latter had to get up close and personal with the .50 cal main armament of the p-51 and p-47. the 20mm hispano carried by the p-38 while for
20_mm_artillery Aircraft_guns Anti-aircraft_guns_of_the_United_States Multi-barrel_machine_guns Rotary_cannons United_States_Marine_Corps_equipment