Warfare Equipment

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 .303 inch (7.7 mm) machine guns commonly used in military aircraft in the 1930s.



Development

The French company, Hispano-Suiza S. A., located in Bois Colombes, France, emerged from World War I as one of the most famous aircraft engine manufacturers in the World. The firm was first organized in France in 1904 as a branch of Spanish La Cuadra automobile firm, formed by artillery captain Emilio de la Cuadra. It was later joined by Swiss engineer Marc Birkigt, the subsequent designer of HS.404.

From Oerlikon to Hispano

In the 1930s Hispano-Suiza took out a licence to build an engine drive shaft version of the Swiss Oerlikon FF S or Becker model, an advanced primer ignition blowback design, fiering from an open bolt. The Oerlikon FF S was based on the Oerlikon 20 mm anti-aircraft auto-cannon. The Hispano-Suiza version was called the "Hispano-Suiza Automatic Cannon Type HS.7" and HS.9. The Swiss cannon, like all pre-war Oerlikon guns, was a recoil-operated weapon with certain unique features; a barrel that does not recoil and a heavy breechblock which is never locked against the breech and actually moves forward when the gun is fired. Shortly after production began, the Hispano-Suiza and Oerlikon companies disagreed over patent rights and their business connection came to an end.

In 1933, Birkigt began work on the design of an entirely new weapon to replace the Oerlikon contract, based on a locking mechanism patented in 1919 by Carl Swebilius (an American machine-gun inventor). The result was the Type 404, or HS.404. While the HS.404 resembled the parent Oerlikon FF S in many respects, its repeating mechanism was gas-operated. When the projectile passes a port cut into the barrel, hot gas behind the projectile is siphoned off and enteres a chamber. There it pressed against a piston. The piston is connected to a rod that unlocks the bolt, allowing the gas pressure in the barrel to drive the bolt backward. Since the bolt was locked during firing, the heavy bolt of the Oerlikon could be replaced by a much lighter one, which greatly increased the rate of fire to 700 rounds per minute, about 200 rounds over the Oerlikon. In 1938 Birkigt patented it and started production in their Geneva factory. In the comparable MG FF (also developed from the Orleikon), the mechanism remained an advanced primer ignition blowback, and lightening of the bolt was only achieved by a lighter charge, which also lowered muzzle velocity. Still, the Hispano retained it's advantage in rate of fire throughout the war compared to the MG FF.

SCREENSHOOT

Type	Aircraft Cannon
Place of origin	France
Service history
Wars	World War II Korean War
Production history
Designer	Marc Birkigt
Manufacturer	Hispano-Suiza
Specifications
Weight	43 kg (94 lb 13 oz)
Length	2.52 m (8 ft 3 in)
Barrel length	80 calibres
Cartridge	20×110 mm
Caliber	20 mm (0.79 in)
Action	gas operated
Rate of fire	700 rounds/min
Muzzle velocity	880 m/s (2,900 ft/s)
Feed system	Drum magazine, belt (later models)