Hispano-Suiza HS.820
Encyclopedia
The Hispano-Suiza
HS.820 was a 20 mm autocannon
developed 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.
Developed in the post-WWII era, the HS.820 fired a 20 × 139 mm round developed from the Swiss 20 x 139 FMK (and FK 38) as a replacement for their earlier 20 x 110 mm design of the widely-used HS.404
. The new round was one of two post-war European 20 mm designs, the other being the 20 × 128 developed by Oerlikon for a similar role. The HS.820's high 1100 m/s muzzle velocity
and equally high 1000 rounds per minute firing rate made it a formidable weapon. Nevertheless, the rapid introduction of even higher performance revolver cannon
s meant the HS.820 was never as popular in aircraft role as the HS.404 had been.
The weapon was more widely used in a variety of mounts for the anti-aircraft role, especially in naval use. Hispano introduced a number of mountings with a variety of sighting systems, feeds and power traverse. The HS.639-B3 (later known as the GAI-CO1) was a single-gun mounting fed from a 75-round drum, a fairly serious limitation for a gun with such a high rate of fire. Variants included the HS.639-B4 (GAI-CO3) with a 50-round drum mounted on top of the weapon, and the HS.639-B5 (GAI-CO6) that used dual 75-magazines for longer firing times. The HS 665 was a triple-mount variety using the same drum feeds. The HS.666A (GAI-DO1), developed in the mid-70s, featured two HS.820 with new 120-round box magazines mounted on a shared hydraulically powered platform which could be tied into an associated radar-guided fire-control system.
The United States produced a slightly modified version of the HS.820 as the M139. It saw use on a number of vehicles, including the US Army's M114 and the Marine Corps
Amphibious Assault Vehicle
and the ill-fated MICV-65
series of armored vehicles. The 20 × 139 mm round was also widely used in a variety of other weapons, including the Rheinmetall MK 20 Rh 202
(Mauser Mk.20) and 20 mm modèle F2 gun
.
Hispano-Suiza
Hispano-Suiza was a Spanish automotive and engineering firm, best known for its luxury cars and aviation engines in the pre-World War II period of the twentieth century. In 1923, its French subsidiary became a semi-autonomous partnership with the parent company and is now part of the French SAFRAN...
HS.820 was a 20 mm autocannon
Autocannon
An autocannon or automatic cannon is a rapid-fire projectile weapon firing a shell as opposed to the bullet fired by a machine gun. Autocannons often have a larger caliber than a machine gun . Usually, autocannons are smaller than a field gun or other artillery, and are mechanically loaded for a...
developed primarily for aircraft use, but more widely used in a series of ground-based anti-aircraft guns. After Oerlikon
Oerlikon Contraves
Rheinmetall Air Defence AG is a division of German armament manufacturer Rheinmetall, created when the company's Oerlikon Contraves unit was renamed on 1 January 2009 and integrated with Rheinmetall's other air-defence products...
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.
Developed in the post-WWII era, the HS.820 fired a 20 × 139 mm round developed from the Swiss 20 x 139 FMK (and FK 38) as a replacement for their earlier 20 x 110 mm design of the widely-used HS.404
Hispano-Suiza HS.404
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...
. The new round was one of two post-war European 20 mm designs, the other being the 20 × 128 developed by Oerlikon for a similar role. The HS.820's high 1100 m/s muzzle velocity
Muzzle velocity
Muzzle velocity is the speed a projectile has at the moment it leaves the muzzle of the gun. Muzzle velocities range from approximately to in black powder muskets , to more than in modern rifles with high-performance cartridges such as the .220 Swift and .204 Ruger, all the way to for tank guns...
and equally high 1000 rounds per minute firing rate made it a formidable weapon. Nevertheless, the rapid introduction of even higher performance revolver cannon
Revolver cannon
A revolver cannon is a type of autocannon commonly used as an aircraft gun. It uses a cylinder with multiple chambers, like those of a revolver handgun, to speed up the loading-firing-ejection cycle. Some examples are also power-driven, to further speed the loading process, but this is by no means...
s meant the HS.820 was never as popular in aircraft role as the HS.404 had been.
The weapon was more widely used in a variety of mounts for the anti-aircraft role, especially in naval use. Hispano introduced a number of mountings with a variety of sighting systems, feeds and power traverse. The HS.639-B3 (later known as the GAI-CO1) was a single-gun mounting fed from a 75-round drum, a fairly serious limitation for a gun with such a high rate of fire. Variants included the HS.639-B4 (GAI-CO3) with a 50-round drum mounted on top of the weapon, and the HS.639-B5 (GAI-CO6) that used dual 75-magazines for longer firing times. The HS 665 was a triple-mount variety using the same drum feeds. The HS.666A (GAI-DO1), developed in the mid-70s, featured two HS.820 with new 120-round box magazines mounted on a shared hydraulically powered platform which could be tied into an associated radar-guided fire-control system.
The United States produced a slightly modified version of the HS.820 as the M139. It saw use on a number of vehicles, including the US Army's M114 and the Marine Corps
Marine corps
A marine is a member of a force that specializes in expeditionary operations such as amphibious assault and occupation. The marines traditionally have strong links with the country's navy...
Amphibious Assault Vehicle
Amphibious Assault Vehicle
The Assault Amphibious Vehicle —official designation AAV-7A1 is a fully tracked amphibious landing vehicle manufactured by U.S. Combat Systems .The AAV-7A1 is the current amphibious troop transport of the United States Marine Corps...
and the ill-fated MICV-65
MICV-65
MICV-65, short for Mechanized Infantry Combat Vehicle, 1965, was a US Army project that studied a number of armored fighting vehicles that would replace the M113 and M114 as well as take on a variety of new roles. A number of designs were studied as part of the MICV project, but none of the entered...
series of armored vehicles. The 20 × 139 mm round was also widely used in a variety of other weapons, including the Rheinmetall MK 20 Rh 202
Rheinmetall MK 20 Rh 202
The Rh202 is autocannon with a calibre of 20 mm designed and produced by Rheinmetall.The cannon is used on military vehicles of German origin, like the Marder infantry fighting vehicle, the Spähpanzer Luchs and some variants of the Wiesel AWC...
(Mauser Mk.20) and 20 mm modèle F2 gun
20 mm modèle F2 gun
- History :The need for a newer 20 mm defence cannon than the Oerlikon 20 mm cannon began to grow noticeably during the 1980s. The companies DCN and GIAT were contracted to design the F2 20 mm cannon, which essentially a navalised version of the M693 gun used by the French Army, and sold for...
.
Original Hispano-Suiza Ammunition
- UIA (HEI) Projectile weight 120 g, Explosive filler 10 g
- RIA (APHEI) Projectile weight 120 g, Explosive filler 4.5 g
- RINT (AP) Projectile weight 111 g, Core weight 70 g