20-mm Oerlikon file photo

20 mm Oerlikon Anti-Aircraft Gun

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


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 bought out by another Swiss company, Werkzeug Maschinenfabrik Oerlikon. During the inter-war years, a series of 20-mm Oerlikon autocannons were built, including the FF, FFL, S, and SS variants.

The 20-mm Oerlikon 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.

The 20-mm Oerlikon autocannons were used by both sides of WW2. During the inter-war years, Japan produced the FF and FFL variants as the Type 99 Model 1 and Model 2 autocannons used by the Japanese Navy, both shipboard as well as with aircraft; for example, the A6M Zero fighters built by Mitsubishi were equipped with them. Meanwhile, Germans built the MG FF and MG FFM autocannons, also based on the FF variant; the famed German Bf 109 fighters were equipped with MG FF autocannons.

The Royal Navy adopted Oerlikon autocannons much later compared to the Germans and the Japanese, not signing a contract with the Swiss firm until 1939. The contract was for 1,500 units, but only 109 units were delivered due to the German invasion of France. However, sensing German threat, Oerlikon approached the British government and asked for permission to relocate its production to the United Kingdom, which was granted immediately. The Royal assisted the company in sneaking technical drawings and other documents out of Zürich, and by end of 1940 British-made 20-mm Oerlikon autocannons were coming off the production line of the new factory at Ruislip, London, England. The first delivery of these British-built Oerlikon autocannons were made to the Royal Navy in Mar or Apr 1941.

Starting in 1942, 20-mm Oerlikon autocannons were being used by the United States Navy as well, replacing the M2 Browning machine gun as the standard short-range anti-aircraft weapon. Although they lacked stopping power against heavy aircraft, they nevertheless played a critical role in the Pacific War, particularly against special attack kamikaze aircraft that often got close to American ships.

Source: Wikipedia.


Close-up view of USS North Carolina20mm Oerlikon crews at the base of one of the main turrets aboard USS North Carolina, 1942; note African-American crewmenAfrican-American mess attendants of USS Copahee posing with the shipAnti-aircraft gunnery drill aboard USS Alabama in the Atlantic Ocean, 1943
See all 30 photographs of 20 mm Oerlikon Anti-Aircraft Gun

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Visitor Submitted Comments

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

  2. Anonymous says:
    23 Mar 2014 06:54:56 PM

    Recent story circulated on the web tells of a B-17 returning to base after a mission with 11 20mm unexploded shells in a fuel tank. Would the Germans have been using this gun against high altitude bombers? I think the story is contrived, but since I know nothing about armaments I won't make a cricism. Thank you.
  3. David Stubblebine says:
    23 Mar 2014 08:37:56 PM

    To #2:
    The story of the B-17 "Tondelayo" of the 379th BG, 527th BS (#42-29896) with 11 unexploded 20mm shells in her fuel tanks traces to the book *The Fall of Fortresses* by the aircraft’s navigator, Elmer Bendiner.
    More to the point, the 20mm MG FF cannon was standard armament on several Luftwaffe front line fighters. This gun was a derivative of the Swiss Oerlikon.
    Also, the standard German anti-aircraft gun was the FlaK 38 (http://ww2db.com/weapon.php?q=c86). The specifications for this gun called it a 2cm gun, which for metric-stupid Americans like me, is exactly 20mm.
    The biggest questions arise as one considers the effective range of the FlaK 38 which is 2,400 yards. As an anti-aircraft gun, the FlaK 38 was intended more for low altitude attack-bombers than for high altitude heavy bombers like the B-17.
  4. George McClellan says:
    24 Mar 2014 11:28:44 AM

    David Stubblebine: Thanks for your response. I have to assume that the B-17 in the story was hit by German fighters. I know that the 20 mm was used for defense against low altitude attacks. I think I'm correct in assuming that it was not used against high altitude attacks. Other than Ploesti, B-29 raids on Japan and a couple of others, I know of no low level (7200') heavy bomber attacks. The story doesn't mention any fighter attacks. Maybe I should get the book.

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