A 30mm GCM-A03-2 seen on a Royal Navy Type 22 frigate.
Source: Royal Navy - © Crown copyright
The Hispano-Suiza HS.831 is an early Cold War era autocannon of Swiss origin. It is a post-war development of the HS.830 developed in 1944. It also shares many similarities with the 20mm HS.820 developed at the same time. Present day it is better known as the Oerlikon KCB. This is the improved HS.831L model in the Oerlikon line-up after Oelikon acquired the armament division of Hispano-Suiza in 1970.
The HS.831 is a single barrel autocannon. It uses a gas unlocked blowback action. Upon firing the gas action unlocks the action, making the blowback action less violent but still powerful enough to cycle the action. This autocannon is uses a magazine feed or a single belt feed mechanism, feeding from either from the left or right. The HS.831L is an updated version developed in the late 1950's to achieve a higher muzzle velocity required in Swiss testing. It fires a new range of ammunition which has lighter projectiles with higher muzzle velocity, extending the practical range as an anti-aircraft gun.
The original HS.831A has a cyclic rate of fire of 600 rpm. This was increased to 650 rpm in the later HS.831L. The ammunition for the HS.831L is ballistically matched for a muzzle velocity at 1.080 m/s. The manufacturer claims an effective range against aircraft of 2.5 km, against surface targets of 3.25 km and the ballistic slant range is about 6 km.
Initial use of the HS.831A was on a tripod mount for anti-aircraft use, introduced around 1955. This was quickly supplemented by the HS.661B mount with much better fire control and smooth traverse, making maximum use of the 2.5 km practical range potential. The French AMX-13 DCA mounts two HS.831A autocannon, as does the larger chassis AMX-30 DCA sold to Saudi Arabia. The HS.831L was also used on a variety of manned naval mounts, sometimes with additional off mount fire control. These include the twin barrel GCM-A, single barrel DS30B and twin barrel Emerlec-30.
Forward view of two 30mm Hispano-Suiza HS.831A autocannon seen on a derelict AMX-13 DCA self-propelled anti-aircraft gun at the Saumur tank museum.
Source: Victor den Bak - © Public domain
An early predecessor of the HS.661B gun mount was fitted with the HS.831A autocannon and was fed by a drum magazine.
The HS.661B single gun anti-aircraft gun is fitted with the HS.831L. Fed by a box magazine holding 8 stripper clips of 5 rounds each.
The French AMX-13 DCA is armed with two HS.831A autocannon.
The AMX-30 DCA is a further development of the AMX-13 DCA using the larger AMX-30 tank chassis.
South Korean self-propelled anti-aircraft gun. Armed with two Oerlikon KCB (HS.831L) autocannon.
Two Oerlikon KCB autocannon are used in the GCM-A series of naval gun mounts. These feature either local or remote control.
Two Oerlikon KCB autocannon are used in the Emerlec 30 naval mount.
A single KCB autocannon is fitted in the DS30B (previously called LS30B) naval gun mount.
The HS.831 uses the same operating mechanism as the 20x139mm HS.820 autocannon. In 1970 this also became part of the Oerlikon product line-up as the KAD.
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