Oerlikon 20 mm cannon
It was widely produced by Oerlikon Contraves and others, with various models employed by both Allied and Axis forces during World War II.Because the Treaty of Versailles banned further production of such weapons in Germany, the patents and design works were transferred in 1919 to the Swiss firm SEMAG (Seebach Maschinenbau Aktien Gesellschaft) based near Zürich.In 1930 Oerlikon reconsidered the application of its gun in aircraft and introduced the AF and AL, designed to be used in flexible mounts, i.e. manually aimed by a gunner.[4] Apart from changes to the design of the guns for wing-mounting and remote control, larger drums were introduced as it would not be possible to exchange magazines in flight.It was not until the Commander-in-Chief of the Home Fleet, Admiral Sir Roger Backhouse, was appointed First Sea Lord that Mountbatten's efforts bore fruit.It became famous in the naval anti-aircraft role, providing an effective defense at short ranges (in practice up to 1.5 km) at which heavier guns had difficulty tracking a target.The gun was eventually abandoned as a major anti-air weapon due to its lack of stopping power against heavy aircraft and against Japanese kamikaze attacks during the Pacific War.[6] It is still in use today on some naval units, nominally as a last-recourse anti-air weapon, but mainly used for firing warning shots or incapacitating small vessels.[citation needed] Unlike most high-powered autocannons, the Oerlikon and its derivatives have a blowback mechanism: the bolt is not locked to the breech of the gun at the moment of firing.[7] In contrast, 20mm cartridges are far too powerful, and efficient autocannon barrels too long, for this basic system to be practical; so the Oerlikon uses Advanced Primer Ignition (API) to augment the resistance of the bolt.Synergistically with this, a second advantage of this unusual arrangement is that after firing the bolt and case have a short, but significant, distance to travel rearwards before the bolt-end re-emerges and the case in turn begins to leave the chamber; and this in combination with the retardation of the rearward travel provides sufficient time for gas pressure to drop to the necessary safe level.[4] This unique chamber and bolt design necessitates the use of a characteristically shaped cartridge: the case has straight sides, very little neck, and a rebated rim.In a typical single-barrel naval version, it is free-swinging on a fixed pedestal mounting with a flat armored shield affording some protection for the crew.[9][10] It was also placed experimentally on the battleships Arkansas, Colorado, Maryland, West Virginia, Washington, Massachusetts, and training ship Wyoming.Although guns with blowback action had played an important part in WW2, it was obvious that something better was needed, especially for the universal demand for a high rate of fire.As a response to this demand, Oerlikon developed "power reserve loading" action,[12] introducing a gas-operated mechanism to unlock the breech.
FrenchAutocannonWorld War IIOerlikonOerlikon FFMG FF cannonkilogramsCaliberActionAPI blowbackElevationTraverseRate of fireMuzzle velocityautocannonsBecker Type M2 20 mm cannonWorld War IOerlikon Contraves20 mm caliber20 mm Beckerrate of fireLuftstreitkräfteanti-aircraftTreaty of VersaillesZürichZürich suburb of Oerlikonflexible mountsHispano-SuizaV-12 enginesIkariaImperial Japanese NavyType 99-1Type 99-2AlliedIMR 4831smokeless powderRoyal NavyDido-classcruiserHMS DidoPZL P.24Messerschmitt Bf 109Type 99 Mark 1 cannonMitsubishiA6M ZeroMorane-Saulnier M.S.406Louis MountbattencaptainCommander-in-ChiefHome FleetAdmiralSir Roger BackhouseFirst Sea Lordfall of FranceRuislipLondonRAF RegimentBoforsEssex-classaircraft carrierUSS HornetUnited States NavyM2 Browning machine gun1.1"/75 caliber gunstopping powerkamikazePacific WarBofors 40 mm3"/50 Mark 22 gunRoyal Canadian NavyU-boatscorvettesfrigatesdestroyersPolstenCromwell tanksCenturion tankswarning shotsblowbackAdvanced Primer IgnitionJapanese 99 Mark 2rebated rimTribal-class destroyerHMCS HaidamagazinepedestalarmoredPT boatsArkansasColoradoMarylandWest VirginiaWashingtonMassachusettsWyomingGAI-B01List of autocannonList of API blowback firearms20mm caliber2 cm Flak 30/38/Flakvierling20 mm modèle F2 gun25 mm Hotchkiss anti-aircraft gunHispano-Suiza HS.404Type 96 25 mm AT/AA gunType 99 cannonArms and Armour PressAnnapolisNaval Institute PressChinn, George M.Bureau of OrdnanceFrauenfeldWilliam Morrow and Co.Ballantine BooksShrewsburyYouTubeOerlikon SSG36Solothurn S-18/100Becker Type M2MK 108 cannonDaewoo K4Heckler & Koch GMGMk 19 grenade launcherQLU-11 (LG5)Atchisson AA-12Sterling SMGQJZ-171