High Quality Content by WIKIPEDIA articles! The Hispano-Suiza HS.404 was an autocannon 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 caliber 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 caliber) and 7.7 mm (.303 caliber) machine guns commonly used in military aircraft in the 1930s.