The Hispano-Suiza HS.404 was an auto cannon widely used as both an aircraft and land weapon in the 20th century by British, American, French, and numerous other military services. The cannon is also referred to as Birkigt type 404, after its designer. Firing a 20 mm calibre projectile, it delivered a useful load of explosive from a relatively light weapon. This made it an ideal anti-aircraft weapon for mounting on light vehicles, as well as a fighter aircraft gun replacing the multiple 7.62 mm (.30 calibre) and .303 inch (7.7 mm) machine guns commonly used in military aircraft in the 1930s.