20-mm Oerlikon file photo [5509]

20 mm Oerlikon Anti-Aircraft Gun

Country of OriginSwitzerland
TypeAnti-Aircraft Gun
Caliber20.000 mm
Length2.210 m
Barrel Length1.246 m
Weight68.000 kg
Rate of Fire450 rounds/min
Ceiling2.000 km
Muzzle Velocity820 m/s



This article deals with the land and ship-based anti-aircraft variants of the Oerlikon 20-millimeter weapon. For the design's aircraft autocannon applications, please see 20 mm MG-FF Oerlikon, Type 99 Mark 1, and Type 99 Mark 2.

During WW1, Reinhold Becker designed a 20-mm autocannon that saw limited use. In 1919, the firm Seebach Machinenbau Aktien Gesellschaft of Switzerland purchased the design, and the company was in turn taken over by another Swiss company, Werkzeug Maschinenfabrik Oerlikon. During the inter-war years, a wide range of variants were built, but it would be the anti-aircraft variant, especially those mounted on naval vessels, that would gain the design its popularity.

These 20-millimeter autocannons were single-barreled weapons operated by blowback. Ammunition was fed through the top, and empty cartridges were ejected from below. The triggers were located on the right handle. The aiming mechanisms were often the simple ring-and-bead sights. They fired explosive rounds that detonated on contact.

In 1937, Louis Mountbatten began voicing support for the introduction of Oerlikon weapons for the British Royal Navy, but it was not until 1939 when newly-appointed First Sea Lord Admiral Roger Backhouse expressed agreement with Mountbatten that the Royal Navy finally placed an order for 1,500 examples. Production delays in 1939 and the German conquest of France in 1940, however, meant the Swiss company could only deliver 109 examples; all of these 109 examples were mounted for land use. In early 1940, Britain purchased the rights to produce these weapons under license, and sent agents to Switzerland to smuggle out the technical drawings. The production of the first British-made Oerlikon autocannon started in Ruislip, London, England, United Kingdom at the end of 1940, and the first British-made guns were delivered to the Royal Navy in Mar or Apr of 1941.

Following the lead of the British Royal Navy, the Royal Canadian Navy also employed Oerlikon autocannon on naval vessels. Because Canadian vessels were often used in anti-submarine roles, there were many instances during which Oerlikon autocannon were depressed so that their explosive shells were used against German submarines sailing on the surface.

On the other side of the Atlantic Ocean, the United States Navy adopted Oerlikon autocannon in 1942. They were without a doubt an upgrade from the M2 Browning machine guns that they replaced, but by this period of WW2, they lacked stopping power against modern aircraft. While the Bofors 40-millimeter guns packed more punch against serious air attacks, Oerlikon autocannon continued to be employed in the US Navy in large numbers.

The Oerlikon design also used as the basis for the Polsten gun, designed by Polish engineers in exile in the United Kingdom. The gun went into service in 1944 and was used well into the 1950s , among other uses, on Cromwell tanks and early model Centurion tanks.

Despite their near obsolesence, Oerlikon autocannon remained in use aboard some naval vessels long after the end of WW2 as the last line of defense against incoming aircraft or missiles.

Source: Wikipedia ww2dbase

Last Major Revision: Jan 2008

20 mm Oerlikon Anti-Aircraft Gun Interactive Map


Close-up view of USS North CarolinaUSS Enterprise gunnery crews practice with their 20mm anti-aircraft guns off Hawaii, May 1942.20mm Oerlikon crews at the base of one of the main turrets aboard USS North Carolina, 1942; note African-American crewmenAfrican-American mess attendants take their turn at a 20mm gun during gunnery training on Aircraft Transport USS Copahee during transit from California to Pearl Harbor, 9 Sep 1942. Note TBF Avengers on the flight deck.
See all 62 photographs of 20 mm Oerlikon Anti-Aircraft Gun

Did you enjoy this article or find this article helpful? If so, please consider supporting us on Patreon. Even $1 per month will go a long way! Thank you.

Share this article with your friends:


Stay updated with WW2DB:

 RSS Feeds

Visitor Submitted Comments

1. Anonymous says:
21 Oct 2009 12:52:12 AM


All visitor submitted comments are opinions of those making the submissions and do not reflect views of WW2DB.

Posting Your Comments on this Topic

Your Name
Your Email
 Your email will not be published
Comment Type
Your Comments


1. We hope that visitor conversations at WW2DB will be constructive and thought-provoking. Please refrain from using strong language. HTML tags are not allowed. Your IP address will be tracked even if you remain anonymous. WW2DB site administrators reserve the right to moderate, censor, and/or remove any comment. All comment submissions will become the property of WW2DB.

2. For inquiries about military records for members of the World War II armed forces, please see our FAQ.

Search WW2DB
20 mm Oerlikon Anti-Aircraft Gun Photo Gallery
Close-up view of USS North Carolina
See all 62 photographs of 20 mm Oerlikon Anti-Aircraft Gun

Famous WW2 Quote
"No bastard ever won a war by dying for his country. You win the war by making the other poor dumb bastard die for his country!"

George Patton, 31 May 1944

Support Us

Please consider supporting us on Patreon. Even $1 a month will go a long way. Thank you!

Or, please support us by purchasing some WW2DB merchandise at TeeSpring, Thank you!