30mm Hispano-Suiza HS.831

Oerlikon KCB


30mm GCM-A03-2

A 30mm GCM-A03-2 seen on a Royal Navy Type 22 frigate.
Source: Royal Navy - © Crown copyright

Entered service
1944 for HS.830 prototype
Early 1950's for HS.831A
Late 1950's for HS.831L
In service
1944 for HS.830 prototype
Late 1940's - Early 1950's for HS.831A
Late 1950's for HS.831L
Switzerland - Hispano-Suiza
1954 - 1960's (HS.831A)
Late 1950's - Present? (HS.831L / KCB)
Switzerland - Hispano-Suiza (up to 1970)
Switzerland - Oerlikon-Contraves (since 1970)
Number produced
At least hundreds
Oerlikon KCB (HS.831L in Oerlikon product lineup)



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.


30mm Hispano-Suiza HS.831A

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

List of HS.831 variants

Early model developed in 1944. Intended for use in aircraft. Used 30x170mm ammunition with brass case. Only produced as prototypes for testing purposes.
Early 1950's development for use in anti-aircraft mount. Fires at 600 rpm and uses steel case ammunition to cope with the pressures and violent case ejection. Tested in a quad mount, but only ever produced in a single gun mount. Also used in the AMX-13 DCA and AMX-30 DCA twin gun self-propelled anti-aircraft guns.
Improved model developed to meet Swiss requirements for a higher velocity anti-aircraft gun. Fires a slightly lighter projectile at higher velocity and higher 650 rpm cyclic rate of fire. Also known as HS.831SLM, possibly only when using a box type clip fed magazine.
Oerlikon KCB
HS.831L became part of the Oerlikon line-up as the KCB after Hispano-Suiza was acquired in 1970. The in the Oerlikon naming convention this means: K = autocannon, C = 30mm caliber, B = second model in this caliber.


Facts HS.831A HS.831L (Oerlikon KCB)
30x170mm (steel cased)
Feed system
Belt feed (either left or right hand feed), drum feed or 5-round stripper clips
Barrel length
2.56 m
18 grooves, right hand twist
Muzzle velocity
970 m/s
Combined gas and blowback operation
Rate of fire
600 rpm
Recoil force
14 kN
Recoil stroke
50 mm
158 kg, possibly including feed mechanism or mount
3.5 m
0.2 m


30mm HS.661 (early model)

An early predecessor of the HS.661B gun mount was fitted with the HS.831A autocannon and was fed by a drum magazine.

30mm HS.661B

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.

K30 Biho

South Korean self-propelled anti-aircraft gun. Armed with two Oerlikon KCB (HS.831L) autocannon.

30mm Oerlikon GCM-A03

Two Oerlikon KCB autocannon are used in the GCM-A series of naval gun mounts. These feature either local or remote control.

30mm Emerlec EE-30

Two Oerlikon KCB autocannon are used in the Emerlec 30 naval mount.

30mm DS30B Mark I

A single KCB autocannon is fitted in the DS30B (previously called LS30B) naval gun mount.

Related articles

20mm Hispano-Suiza HS.820

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.