Oerlikon 20 mm cannon
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| Calibre: | 20 mm |
| Weight of round: | 0.123 kg |
| Mass of the system: | 480 kg (without ammunition) |
| Elevation: | -15° to + 90° |
| Maximum practical range: | 2000 m against aerial targets |
| Muzzle velocity: | 820 m/s |
| Rate of fire: | 450 round/min |
History
The German Army was the first user, mounting it on its aircraft during the First World War. In 1919, the patent was transferred to Switzerland, and production assumed by Semag, later bought by Werkzeug Maschinenfabrik Oerlikon. Most of the main parties of the Second World War bought licenses to manufacture the cannon themselves.In 1935, the cannon was adapted by Britain to be used in the Royal Navy for the short-range anti-aircraft role. It was fielded in United States Navy ships starting in 1942, replacing the 1.1" Mark 1 autocannon, to which it was much superior. It came to be famous in the naval antiaircraft role, notably against Japanese kamikaze attacks during the Pacific War. The gun was eventually abandoned as a major anti-air weapon due to its lack of stopping power against heavy aircraft, largely superseded by the Bofors 40 mm gun.
It is still in use today on some naval units, theoretically as a last-recourse anti-air weapon, but mainly used for police shots (warning shots or incapaciting shots).
The Polsten gun was based on the Oerlikon.
Description
The Oerlikon 20 mm cannon is a monotube cannon with a large coil around it.
In its naval version, it is fixed on a free-swinging mount, and a flat armor shield gives some protection for the crew. The cannon is manned by the gunner (who aims and fires the piece), the piece chief (designating objectives), and the feeder (supplying fresh ammunition).
The gun is manoeuvered by the gunner, who is attached to the weapon. The fire is directed through an optical visor, the same as used on the Bofors 40 mm gun.
Ammunition feed is by a cylindrical magazine on the top of the gun. A trigger in the right-hand grip controls fire. Used cartridges are ejected from below the breech. During sustained firing, the 60-round magazine must be frequently changed by hand by the feeder, reducing the effective rate of fire.
References
- Campbell, John. Naval Weapons of World War Two. Annapolis: Naval Institute Press, 1985.
See also
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