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Oerlikon 20mm Cannon
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.
Specifications
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:
Film
| 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 |
Television
| Show Title | Actor | Character | Note / Episode | Air 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 |
Anime
| 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 |
Animation
| Title | Character | Note | Date |
|---|---|---|---|
| Archer | German Sniper | "Heart of Archness, Part I" (S03E01). | 2011-2012 |