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Oerlikon 20mm Cannon

From Internet Movie Firearms Database - Guns in Movies, TV and Video Games
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US Navy single pedestal mount Oerlikon Mark 4 cannon with early-war eyepiece / ring antiaircraft sight - 20x110mm RB. This crude AA sight was replaced with the much more advanced Mark 14 Gyro Gunsight (a reflector sight with automatic target lead calculation) starting in 1943, with the improved Mark 20 replacing the Mark 14 postwar.
Twin Oerlikon Mark 4 cannons in a Mark 24 mounting with Mark 14 Gyro Gunsight - 20x110mm RB. Note markings on left-handed snail drum.
20 mm Polsten - 20x110 RB. This is a simpler variant of the original model. It has half as many pieces as the original.

The Oerlikon 20mm cannons are a series of Swiss-designed 20mm API blowback operated autocannons based directly on the WW1-era Becker machine gun's descendant, the SEMAG-L. After the failure of Becker's company SEMAG in the interwar years, the Zürich-based Oerlikon company acquired all rights to the design and in the mid-1920s began production of the Oerlikon F, Oerlikon L, and Oerlikon S; these three were the same basic design, progressively scaled up in longer 20mm cartridges.

In 1935 the US Navy purchased two of the current model of Oerlikon for trials; they were rejected, almost bankrupting Oerlikon until they hit on the idea of designing a series of shortened derivatives for mounting in the wings of fighter aircraft, these being the FF F, FF L, and FF S. In an ironic (with hindsight) twist, the company was saved when the Imperial Japanese Navy bought production rights to the FF F and FF L, developing them into the Type 99 Mark 1 and Type 99 Mark 2, respectively; the Germans also developed the FF F into the MG FF.

The Royal Navy rejected the same model of Oerlikon that had previously been offered to the US Navy in 1937, but stated that, if the muzzle velocity could be raised they would be interested. After this, Oerlikon developed a new iteration of the original cannon making use of the improvements from the FF series, resulting in the SS in 1938. The Oerlikon SS would be the design adopted and used extensively by the Americans and British during WWII. The British adopted the SS as the Mark I in 1939, but only around 100 of these guns arrived in England before the annexation of France by Nazi Germany cut off the supply route, but by this point the Royal Navy had acquired the production diagrams. The British spent considerable time modifying the labor-intensive Mark I, coming up with their domestic Mark II gun in 1941.

The US Navy, looking to replace obsolete AA armament consisting mostly of unreliable 1.1"/75 caliber gun quadmounts and .50 caliber water-cooled Browning M2s with insufficient range or power to shoot down period aircraft, became interested in the British work and designed their own Mark 2 gun in 1941. Over the course of the war the gun was repeatedly reworked to maximize production speed, cutting the 428.4 man-hours per gun in 1941 down to 76.2 hours by September 1944. In 1943 the USN began to equip their Oerlikons with the cutting-edge electromechanical Mark 14 Gyro Gunsight, making them even more effective (the same device was also used on standalone pedestal mounts to direct 1.1"/75 caliber and 40mm guns: in this application it was called the Gun Director, Mark 51). The various Oerlikon variants (mostly the Mark 4 gun, which eliminated the barrel cooling ribs of earlier American variants, was built to Imperial rather the metric standard measurements, and featured only a single heavy buffer spring) proved extremely effective in the Pacific War with 32% of all Japanese aircraft shot down between December 1941 and September 1944 being taken down by Oerlikon guns, and was the primary AA gun on American warships until the Bofors 40mm became available in large numbers in 1943, only beginning to lose effectiveness with the rise in Japanese use of Kamikaze attacks which led to a strong preference for the 40mm Bofors in 1944-45.

By the end of the war the British had manufactured some 55,000 guns while the United States had built a total of 124,735. The Oerlikon was also used by the German Kriegsmarine as the FlaK 28 and FlaK 29. Oerlikons were typically pedestal mounted on warships, either as single or dual mounts which were often manually aimed but sometimes power-assisted. Left-handed guns required special left-handed snail drums, which featured distinctive markings to prevent loading mistakes. Experiments were made with other mounts including a British attempt at designing a belt-fed variant, the uncommon USN Mark 15 quadmount and a USN triple mount which never left the prototype phase due to problems loading the middle gun. Following the war it was a common sight on smaller ships such as PT boats, and is still mounted on some warships today, with British auxiliary ships carrying Oerlikons as late as 2006. When the USN liquidated their vast stockpiles of surplus Oerlikons in the 1950s, most were scrapped or sent overseas but a few ended up on the civilian marked as transferable NFA weapons, and some of these authentic fully-automatic weapons do exist in the hands of movie armorers.

The other gun known as the Oerlikon 20mm is the 20mm Oerlikon KAA, also known as the Oerlikon L/85. This gun was developed in the 1950s but not really common until after the Falklands War renewed interest in light warship armament. This page, however, is for the L/70 version.


Oerlikon SS

(1939-present (US production 1940-1945))

  • Caliber: 20x110mm RB
  • Weight: 1,695 lbs (768.8 kg) (complete USN Mark 2 or 4 single mount), 150 lbs (68 kg) (gun only)
  • Length: 87 in (221 cm)
  • Barrel Length: 55.1 in (140 cm)
  • Capacity: 60 round snail drum, 100-round version also available postwar
  • Fire modes: original SS featured semi or auto, US/British variants auto-only, cyclic 450 rounds per minute, practical 250-320 rounds per minute
  • Effective range: 1,000 yards (914m) against aircraft with HE-I Mark 3 shell, USN Oerlikon gunners typically opened fire at 1,200-1,300 yards (1,097-1,189m) for aiming correction (absolute maximum range 4,800 yards (4,389m) elevated at 45 degrees: AA ceiling 10,000 feet (3,048m))

The Oerlikon 20mm Cannon and variants can be seen in the following films, television series, video games, and anime used by the following actors:


Title Actor Character Note Date
The Fighting Seabees US Marine 1944
Hong Kong on coast guard cutter 1952
The Beast from 20,000 Fathoms US National Guards 1953
Above Us the Waves Mounted on German patrol boat 1955
Soldier of Fortune Clark Gable Hank Lee Mounted on Lee's junk 1955
Blue Arrow (Golubaya strela) Mounted on a submarine 1958
The Guns of Navarone Mounted on German patrol boat 1961
Gorgo Mounted on US Navy submarine 1961
The Longest Day German soldiers 1962
Diamonds Are Forever SPECTRE operatives Mounted on oil rig 1971
Murphy's War German sailors Mounted on the unnamed German U-boat 1971
Thunderbolt and Lightfoot Clint Eastwood Thunderbolt 1974
Midway Mounted on US Navy ships 1976
The Eagle Has Landed Mounted on a German boat 1976
Soldier of Orange Mounted on Royal Navy fast boat; German coastal defence 1977
Concorde Affaire '79 Single mount on French patrol boat P659 Canopus 1979
Uncommon Valor 1983
Rambo III Richard Crenna Colonel Trautman Acetylene Gas Mockup 1988
Return from the River Kwai Mounted on US Navy submarine 1989
The Manchurian Variant (Manchzhurskiy variant) seen in documentary footage of Pacific War 1989
Mediterraneo Mounted on Italian Royal Navy ship on twin mounting, with Mark 14 Gyro Gunsight 1991
Hot Shots! Part Deux The Iraqi Navy Officer Custom version 1993
The Postman The Holnists 1997
The Thin Red Line Mounted on US Navy ship on twin mounting 1998
U-571 Mounted on US Navy submarine 2000
Pearl Harbor Mounted on USS Texas 2001
Captain Corelli's Mandolin German soldiers Mounted on German landing crafts' 2001
Below mounted on the deck of the USS Tiger Shark 2002
Stealth Defenders of mountain fortress 2005
Flags of Our Fathers Mounted on US Navy ship 2006
The Curious Case of Benjamin Button Mounted on German U-boat 2008
X-Men: First Class Mounted on US Navy ship on twin mounting 2011
Emperor 2013
Hunting the Phantom Mounted on the ship 2014
Dunkirk mounted on the British Motor Torpedo Boat and the Destroyer Maillé-Brézé 2017


Show Title Actor Character Note / Episode Date
Airwolf Libawe soldiers "And They Are Us" (S1E09) 1984
Loki - Season 1 USS Eldridge sailors Mounted on USS Eldridge; "Journey Into Mystery" (S1E05) 2021

Video Game

Game Title Appears as Mods Notation Release Date
Medal of Honor: Frontline Kriegsmarine FlaK 29 on the loading screen for Level 1 of The Hornets Nest (Mission 6) 2002
Medal of Honor: European Assault Mounted on the HMS Campbeltown 2005
Call of Duty: World at War Mounted on PBY Catalina 2008
Company of Heroes 2 Twin-mounted on Centaur AA Mk. II Cruiser Tank 2013
Grand Theft Auto V mounted on Half-Track 2013
Rainbow Six Siege Unusable; seen on photo 2015
Call of Duty: WWII 2017
Battlefield V Mounted in Valentine AA tank 2018
Call of Duty: Vanguard Unusable; mounted on aircraft carrier 2021
Enlisted Oerlikon Mark 4 2021
20 mm Polsten


Title Character Note Date
The Cockpit U.S. Navy sailors Ep. 2 "Sonic Boom Squadron"; mounted on American aircraftcarrier 1993
Rebuild of Evangelion Misato's Iowa-class battleships 2007-2012
Strike Witches 2 Single mounts on Fletcher-class destroyers 2010
Strike Witches: Operation Victory Arrow Single mounts on Liberty ships 2014-2015
Brave Witches Single mounts on Liberty ships 2016-2017
Strike Witches: Road to Berlin Single mounts on Liberty ships 2020
Luminous Witches Single mounts on Sangamon-class carrier 2022


Title Character Note Date
Archer German Sniper "Heart of Archness, Part I" (S03E01). 2011-2012

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