Hispano-Suiza HS.820

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HS.820
Swiss HS.820 in the HS.666A configuration.
Type	Autocannon
Place of origin	Swiss
Specifications
Mass	66 kg (146 lb) (without ammunition)
Length	2,489 mm (98.0 in)
Barrel length	1,727 mm (68.0 in)
Caliber	20×139 mm
Action	Gas unlocked, delayed blowback
Rate of fire	1000 round/min
Muzzle velocity	1,050 m/s (3,400 ft/s)
Effective firing range	1,500 m (4,900 ft) against aerial targets

The HS.820 is a 20 mm caliber autocannon developed by Hispano-Suiza primarily for aircraft use, but more widely used in a series of ground-based anti-aircraft guns. After Oerlikon purchased Hispano's armaments division in 1970, the HS.820 became the Oerlikon KAD, supplanting Oerlikon's own KAA and KAB weapons in the process.^[1] A US-built model, the M139, saw some use on vehicles.