The Oerlikon 20 mm cannon is a series of autocannons, based on an original German 20 mm Becker design that appeared very early in World War I. It was widely produced by Oerlikon Contraves and others, with various models employed by both Allied and Axis forces during World War II, and many versions are still in use today.
|Oerlikon 20 mm cannon|
A modern Oerlikon cannon (Oerlikon 20mm/85 KAA) on a Royal Navy warship
|Place of origin||Switzerland|
|Wars||World War II, various|
|No. built||124,734*"20mm Oerlikon Light Antiaircraft Gun". Retrieved 30 May 2019.|
MG FF cannon
|Shell weight||HE: 123 g (4.3 oz)|
HE/T: 116 g (4.1 oz)
|Caliber||20 mm (0.79 in)|
|Barrels||Single barrel (progressive RH parabolic twist, 9 grooves)|
|Elevation||Manual training, typically able to depress to -15° and elevate to +90°|
|Traverse||Manual training, full 360°|
|Rate of fire||L70:
|Muzzle velocity||L70: 820 m/s (2,700 ft/s) L85: 1,050 m/s (3,400 ft/s)|
|Effective firing range||Against low-flying aircraft (HE round)
|Maximum firing range||HE round at 45°
During World War I, the German industrialist Reinhold Becker developed a 20 mm caliber cannon, known now as the 20 mm Becker using the Advanced Primer Ignition blowback (API blowback) method of operation. This used a 20×70mmRB cartridge and had a cyclic rate of fire of 300 rpm. It was used on a limited scale as an aircraft gun on Luftstreitkräfte warplanes, and an anti-aircraft gun towards the end of that war.
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. SEMAG continued development of the weapon, and in 1924 had produced the SEMAG L, a heavier weapon (43 kg) that fired more powerful 20×100mmRB ammunition at a slightly higher rate of fire, 350 rpm.
In 1924 SEMAG failed. The Oerlikon firm, named after the Zürich suburb of Oerlikon where it was based, then acquired all rights to the weapon, plus the manufacturing equipment and the employees of SEMAG.
In 1927 the Oerlikon S was added to the existing product line. This fired a still larger cartridge (20x110RB) to achieve a muzzle velocity of 830 m/s (versus 490 m/s for the original Becker 20x70RB gun), at the cost of increased weight and a reduced rate of fire (280 rpm). The purpose of this development was to improve the performance of the gun as an anti-tank and anti-aircraft weapon, which required a higher muzzle velocity. An improved version known as the 1S followed in 1930.
Three sizes of gun with their different ammunition and barrel length, but very similar mechanisms, continued to be developed in parallel. 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. The 15-round box magazine used by earlier versions of the gun was replaced by drum magazine holding 15 or 30 rounds.
In 1935 it made an important step by introducing a series of guns designed to be mounted in or on the wings of fighter aircraft. Designated with FF for Flügelfest meaning "wing-mounted", these weapons were again available in the three sizes, with designations FF, FFL and FFS. The FF fired a slightly larger cartridge than the AF, 20x72RB, but the major improvement in these weapons was a significant increase in rate of fire. The FF weighed 24 kg and achieved a muzzle velocity of 550 to 600 m/s with a rate of fire of 520 rpm. The FFL of 30 kg fired a projectile at a muzzle velocity of 675 m/s with a rate of fire of 500 rpm. And the FFS, which weighed 39 kg, delivered a high muzzle velocity of 830 m/s at a rate of fire of 470 rpm.
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. For the FF series drum sizes of 45, 60, 75 and 100 rounds were available, but most users chose the 60-round drum.
The 1930s were a period of global re-armament, and a number of foreign firms took licenses for the Oerlikon family of aircraft cannon. In France, Hispano-Suiza manufactured development of the FFS as the Hispano-Suiza HS.7 and Hispano-Suiza HS.9, for installation between the cylinder banks of its V-12 engines. In Germany, Ikaria further developed the FF gun as the MG FF, firing 20x80RB ammunition. And the Imperial Japanese Navy, after evaluating all three guns, ordered developments of the FF and FFL as the Type 99-1 and Type 99-2.
The incorporation of the improvements of the FFS in a new anti-aircraft gun produced, in 1938, the Oerlikon SS. Oerlikon realized further improvements in rate of fire on the 1SS of 1942, and the 2SS of 1945 which achieved 650 rpm. However, it was the original SS gun which was widely adopted as anti-aircraft gun, being especially widely used by Allied navies during World War II.
The Oerlikon FF was installed as armament on some fighters of the 1930s, such as the Polish PZL P.24G. Locally produced derivatives of the Oerlikon cannon were used much more extensively, on aircraft, on ships and on land. In the air, the Ikaria MG FF was used as armament on a number of German aircraft, of which the most famous is the Messerschmitt Bf 109. The Japanese Navy similarly used their copy of the FF, designated the Type 99 Mark One cannon on a number of types including the Mitsubishi A6M Zero. Later in the war, they also equipped fighters including the Zero with the Type 99 Mark Two, a version of the more powerful and faster-firing Oerlikon FFL.
The French firm of Hispano-Suiza was a manufacturer of aircraft engines, and it marketed the moteur-canon combination of its 12X and 12Y engines with a H.S.7 or H.S.9 cannon installed between the cylinder banks. The gun fired through the hollow propeller hub, this being elevated above the crankcase by the design of the gearing. Such armament was installed on the Morane-Saulnier M.S.406 and some other types. Similar German installations of the MG FF were not successful.
The Oerlikon became best known in its naval applications. Initially the Oerlikon was not looked upon favorably by the Royal Navy as a short-range anti-aircraft gun. All through 1937-1938 Lord Louis Mountbatten, then a Captain in the Royal Navy, waged a lone campaign within the Royal Navy to set up an unprejudiced trial for the Oerlikon 20 mm gun, but it was all in vain. 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. During the first half of 1939 a contract for 1,500 guns was placed in Switzerland. However, due to delays and then later the Fall of France in June 1940, only 109 guns reached the United Kingdom. All Oerlikon guns imported from Switzerland, in 1940, were mounted on various gun carriages to serve as light AA-guns on land.
Just a few weeks before the Fall of France, the Oerlikon factory approved manufacture of their gun in the United Kingdom, under licence. The Royal Navy managed to smuggle out the necessary drawings and documents from Zürich. The production of the first British-made Oerlikon guns started in Ruislip, London, at the end of 1940. The first guns were delivered to the Royal Navy in March or April, 1941. The RAF Regiment made extensive use of Oerlikon guns in the anti-aircraft role. These were the principal armament for its Light Anti-Aircraft squadrons in North Africa, the Middle East, Italy, and North Western Europe, until the introduction of the Bofors 40/L60 40mm gun from 1943, although many squadrons retained a mix of guns until the end of World War 2. Squadrons in the Far East were equipped exclusively with Oerlikons.
The Oerlikon gun was installed aboard United States Navy ships from 1942, replacing the M2 Browning machine gun, which lacked range and firepower, and largely superseding the 1.1"/75 caliber gun, which was heavier and had less mechanical reliability. 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. It was largely superseded by the Bofors 40 mm gun and the 3"/50 Mark 22 gun. It provided a useful increase in firepower over the .50 cal machine gun when adapted and fitted to some aircraft. However, it had some problems with jamming in the ammunition feed.
The Royal Canadian Navy popularized the use of the Oerlikon gun as an anti-ship and anti-submarine gun - while it was not effective against the armour of most larger ships, it was used extensively and effectively against U-Boats, and on the decks of larger ships. A handful of corvettes were fitted with the weapon toward the end of the war, but it appeared more commonly on frigates and destroyers at the time.
The Oerlikon was 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.
Romania purchased 45 pieces from Germany during the first half of World War II.
It is still in use today on some naval units, theoretically as a last-recourse anti-air weapon, but mainly used for firing warning shots or incapacitating small vessels.
Very unusually for a high-powered autocannon, the Oerlikon and its derivatives feature blowback operation: the bolt is not locked to the breech of the gun at the moment of firing. Non-locking, simple blowback designs are commonplace in much lighter weapons, such as small-caliber semi-automatic pistols. No locking is required, as with such low-power cartridges the static inertia of the bolt or bolt and slide - the physical tendency of heavy components to resist rapid acceleration - is adequate to ensure that the projectile has left the muzzle and the gas pressure in the barrel is down to a safe level before the breech opens (while the bolt spring also resists the opening of the breech, in practical terms its contribution is too small to be relevant). In contrast, 20mm cartridges are far too powerful, and 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. In API blowback weapons, the firing pin fires the cartridge while the bolt is still traveling forward so that the gas pressure has to overcome the forward momentum of the bolt as well, before it can push it to the rear. To facilitate this, the Oerlikon's chamber is longer than needed to contain the cartridge, and the end of the bolt, which is the same diameter as the case, actually enters this extended chamber behind the cartridge before firing. As a result, when firing occurs, the forward force of the bolt and spring acts against the force of the propellant gases until the latter overcome the former and start pushing case, bolt and spring backwards. If the bolt had stopped at the mouth of the chamber as in a simple blowback gun, this momentum would be neutralized and the additional forward oppositional force would not exist. 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—providing more time for gas pressure to drop to the necessary safe level. This system permits blowback to be used in far more powerful weapons than normal. Nevertheless, compared to guns with a locking mechanism a fairly heavy bolt must be employed; while to give this heavy bolt sufficient forward speed, a large spring is required (and Oerlikons, distinctively, have this component wrapped around their barrels.) These features will limit the rate of fire of such guns, unless other steps are taken—as in the final model of the Japanese 99 Mark 2.
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. The straight sides allows the case to slide back and forward in the cylindrical chamber. The neck is not supported while this happens and therefore expands when the case is fired, and the rebated rim allows the face of the bolt, with its extractor claw hooked over the rim, to fit within the chamber. To ease the motion of the case, the ammunition needed to be greased, which was a drawback of the Oerlikon cannon. An alternative developed during World War II was the so-called fluted chamber, which had grooves that allowed propellant gas to seep between the chamber wall and the case, taking over the role of the grease.
Ammunition feed is typically by a 60-round drum magazine on the top of the gun. During sustained firing, the magazine must be frequently changed, reducing the effective rate of fire. Belt-fed versions of the gun were developed to overcome this limitation. A trigger in the right-hand grip controls fire. Used cartridges are ejected from below the breech.
Different nations and services operated a number of mounting types for the same basic gun. 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. The cannon is aimed and fired by a gunner using, in its simplest form, a ring-and-bead sight. The gunner is attached to the weapon by a waist-belt and shoulder supports. For this reason, some mountings existed with a height-adjustment feature to compensate for different sized gunners. A "piece chief" designates targets and the feeder changes exhausted magazines.
During World War II, twin and quadruple Oerlikon mounts were developed, both for army and for navy use. The British Navy operated a hydraulically operated twin-gun mount. The US Navy operated a quad mount developed for PT boats by Elco Naval Division, Electric Boat Company, called the Elco "Thunderbolt" Mount. Prototypes were built and tested in late 1942 and operationally deployed on several Elco PT Boats in the Mediterranean. It was also placed experimentally on the battleships Arkansas, Colorado, Maryland, West Virginia, Washington, Massachusetts, and training ship Wyoming.
The 20 mm modèle F2 gun is a naval defence weapon used by the French Navy. It was developed from the GIAT M693. It fires the 20×139 mm round originally developed for the Hispano-Suiza HS.820 series.Active Royal Navy weapon systems
This is a list of Active Royal Navy weapon systems.Becker Type M2 20 mm cannon
The Becker Type M2 20 mm cannon was a German autocannon developed for aircraft use during World War I by Stahlwerke Becker. It was first mass-produced in 1916 and was installed in a variety of aircraft. It was the only German autocannon to see service in the air during the war.The Becker also served as the pattern for the famous Swiss-built Oerlikon 20 mm cannon, which is in service to this day, and in a later form, was the original inspiration, through the Swiss design after World War I, for the World War II German Luftwaffe's MG FF (Maschinengewehr Flügel Fest, "fixed wing-mount automatic ordnance") 20 mm autocannon design.Dominican Navy
The Navy of the Dominican Republic or Armada de Republica Dominicana (ARD), is one of the three branches of the Military of the Dominican Republic, together with the Army and the Air Force.HMS Dittisham (M2621)
HMS Dittisham was one of 93 ships of the Ham-class of inshore minesweepers built for the British Royal Navy. Their names were all chosen from villages ending in -ham. The minesweeper was named after Dittisham in Devon.HMS Hound (J307)
HMS Hound was a reciprocating engine-powered Algerine-class minesweeper built for the Royal Navy during the Second World War. She survived the war and was scrapped in 1962.HMS Loyal (G15)
HMS Loyal was a L-class destroyer built for the Royal Navy in the late 1930s, although she was not completed until after World War II had begun.HMS Maenad (J335)
HMS Maenad was a reciprocating engine-powered Algerine-class minesweeper built for the Royal Navy during the Second World War. She survived the war and was scrapped in 1957.HMS Pickle (J293)
HMCyS Parakrama, was an Algerine-class minesweeper of the Royal Ceylon Navy, originally built as HMS Pickle (J293) for the Royal Navy during World War II, and transferred to Ceylon by the United Kingdom in 1958. She was scrapped in 1964.HMS Providence (J325)
HMS Providence was a reciprocating engine-powered Algerine-class minesweeper built for the Royal Navy during the Second World War. She survived the war and was scrapped in 1958.HMS Welcome (J386)
HMS Welcome was a reciprocating engine-powered Algerine-class minesweeper built for the Royal Navy during the Second World War. She survived the war and was scrapped in 1962.LÉ Setanta (A15)
LÉ Setanta (A15) was an auxiliary ship and training ship in the Irish Naval Service. She was named after Sétanta (Cú Chulainn), a mythical hero of the Ulster Cycle.Liffey Dockyard in Dublin built her in 1953 as a lighthouse tender for the Commissioners of Irish Lights. She was launched as Isolde, named after the mythical Irish princess Iseult.
In 1976 the INS bought her, had her armed with two Oerlikon 20 mm cannon and renamed her Setanta. She served until 1984 when the INS sold her to Haulbowline Industries Ltd of Cork for scrap.Oerlikon FF
The FF were a series of 20mm autocannon introduced by Oerlikon in the late 1920s. The name comes from the German term Flügel Fest, meaning wing mounted, fixed, being one of the first 20mm guns to be small and light enough to fit into a fighter aircraft's wing. The FF series inspired many 20mm cannon used in World War II, including the Hispano-Suiza HS.404 (adopted by the French, British and U.S. forces), the German MG FF, and the Japanese IJNAS's Type 99 cannon.
The basic design was based on the original Oerlikon 20 mm cannon, in turn based on the German Empire's Becker 20 mm cannon of World War I. In the post-war period, Oerlikon had developed the original design to produce three autocannons with increasingly powerful rounds; the original model, later known as the "F", used the Becker 20x70mm round, the newer "L" model used a 20x100 round, and finally the "S" model used a 20x110. All of these weapons used the API blowback operational principle.
In 1935 Oerlikon started development of versions suitable for use as wing-mounted guns. In addition to various changes needed for remote firing and cartidge ejection, the new series focused primarily on rate-of-fire. The original "FF" used a slightly upgraded 128 gram 20x72mm round with a muzzle velocity of 600 metres per second (2,000 ft/s) at a cyclic rate of 520 rounds per minute, almost double that of the original F and AF models. The gun weighed only 24 kilograms (53 lb). Similar improvements led to the 30 kilograms (66 lb) FF L using a longer 20x101mm round which gave 750 metres per second (2,500 ft/s), and the 39 kilograms (86 lb) FF S firing a 20x110mm round at 830 metres per second (2,700 ft/s) at a slightly slower 470 rounds per minute. The original guns became known as the FF F from this point on.
The FF F was licensed by the Japanese and produced as the Type 99-1, along with the FF L as the Type 99-2. Hispano-Suiza built the FF S as the HS.7, and slightly improved HS.9. This design was later abandoned by Hispano-Suiza. In the 1930s, Marc Birkigt designed an entirely new gas-operated cannon with a locked bolt, the HS.404, which became one of the best 20 mm weapons of the war. Ikaria Werke in Germany started production of the FF F with a slightly more powerful 20x80mm round as the MG FF, but later introduced a new Minengeschoss round which was lighter and improved velocity. The resulting MG FF/M was a common weapon until about 1944. Starting in late 1940 these were replaced by the very different Mauser MG 151/15 and Mauser MG 151/20 autocannon, respectively of 15mm (early) and 20mm calibre (primary production).Osprey 55-class gunboat
The gunboat class Osprey 55 is a Danish-designed class of naval ship currently in service in the Hellenic Navy and Royal Moroccan Navy. Two ships were ordered by Greece in March 1988 and built by Hellenic Shipyards. The first one was laid down on 8 May 1989 and launched on 19 December 1989. The second ship was laid down on 9 November 1989 and launched on 16 May 1990. Armament is of modular design and therefore can be changed. 76-mm guns replaced the Bofors 40-mm in 1995, after being taken from decommissioned Gearing-class destroyers. Options on more of the class were shelved in favour of the slightly larger HSY-55 class.
4 other ships were ordered by the Royal Moroccan Navy all received between 1987 and 1990. Built in Frederikshavn, Denmark, they were only armed with 1 Bofors 40 mm and 2 Oerlikon 20 mm cannon. El Lahiq is equipped with a cartographic sonar and North American navigation systems for Hydrographic researches.Royal Fleet Auxiliary
The Royal Fleet Auxiliary (RFA) is a naval auxiliary fleet owned by the United Kingdom's Ministry of Defence and is one of the five fighting arms of the Royal Navy. Its purpose is to support the Royal Navy to maintain operations around the world. Its primary role is to supply the Royal Navy with fuel, ammunition and supplies, normally by replenishment at sea (RAS). It also transports Army and Royal Marine personnel, as well as supporting training exercises, and engaging in anti-piracy, anti-drug smuggling, and humanitarian operations.
The RFA counts an Aviation Training ship/Hospital Ship and landing vessels amongst its assets. RFA personnel are employees of the Ministry of Defence, and since 2003, special members of the Royal Naval Reserve deemed sponsored reserves, which are civilians who must be part of the Armed Forces in some capacity, in order to carry out specialist civilian jobs in a military capacity. Although RFA officers wear Merchant Navy rank insignia with naval uniforms, they are classed as a part of the naval service and are under naval discipline when the vessel is engaged on warlike operations. RFA vessels are commanded and crewed by these officers and ratings, augmented with regular and reserve Royal Navy personnel to perform specialised military functions such as operating and maintaining helicopters or providing hospital facilities. Royal Navy personnel are also needed to operate certain weapons, such as the Phalanx, however other weapons (such as the GPMG, Oerlikon 20 mm cannon, 30mm cannon and the 7.62 minigun) are operated by RFA personnel.Super Dvora Mk II-class patrol boat
The Super Dvora Mark II-class patrol boats is a high-speed class of patrol boats meant for a variety of naval missions from typical off-shore coastal patrol mission profiles to high-speed, high-maneuver littoral warfare. Built by Israel Aerospace Industries for the Israeli Sea Corps, the Super Dvora Mark II is the successor to the Dvora-class fast patrol boats. The Super Dvora Mark IIs have been employed by the Sri Lanka Navy to counter LTTE operations at sea.T1 tanker
The T1 tanker or T1 are a class of sea worthy small tanker ships used to transport fuel oil before and during World War II, Korean War and Vietnam War. The T1 tanker classification is still in use today. T1 tankers are about 200 to 250 feet in length and are able to sustain a top speed of about 12 knots. The hull designation AO is used by the US Navy to denote the ship is a T1 oil tanker and AOG that the T1 is a gasoline tanker. The small size allows the T1 to enter just about any sea port or to anchor around a small island, this was very useful during the Pacific War. The T1 tanker can carry about 48,000 to 280,000 BBLs. Some T1 tankers were used to transport goods other than oil, a few were used for black oil-crude oil, diesel, chemicals and rarely bulk cargo like grain. T1 tankers are also called liquid cargo carriers. The T1 tanker has about a 6,000 to 35,000 DWT of cargo. The small size also gives the ships short turn around time for repair, cleaning, loading and unloading. A T1 tanker carrying dirty cargo, like crude oil needs a few weeks of labor to clean before carrying clean cargo. Most T1 ships during World War II were named after major oil fields. T1 tanker are operated by the US Navy, War Shipping Administration and United States Maritime Commission. Some T1 were loaned to England in the Lend-Lease program for World War II, after the war most were returned to the USA. After World War II many of the T1 ships were sold to for civilian use. Each T1 had emergency life rafts on the boat deck. The ships had cargo booms and piping to load and unload fuel. During war time the T1 are armed for protection with deck guns. A typical ship may have one single 3"/50 dual purpose gun, two 40 mm guns and three single Oerlikon 20 mm cannon. A T1 at war time normally had a crew of 38 and up to 130. If operating as a United States Merchant Marine ship, the crew would be a mix of civilian Merchant Marines and United States Navy Armed Guards to man the guns.TCG Sultanhisar (1940)
TCG Sultanhisar was a Demirhisar-class destroyer built for the Turkish Navy during the Second World War. The design of her class was based on the British I class.Vosper 73 ft motor torpedo boat
The Vosper 73 foot motor torpedo boat was a mid-twentieth century British military boat design by Vospers.
At 73 ft (22 m) long they were considered small boats compared to longer designs such as the Fairmile Type D. The design came about from a requirement that British Motor Torpedo Boats should be better able to fight small craft, which was the job of Motor Gun Boats. To this end Vospers built on their existing 70 foot designs. The Type I was introduced in 1943 and the Type II before the end of the Second World War.
The boats carried four 18-inch torpedo tubes as their major offensive armament along with Oerlikon 20 mm cannon and some defensive armament (Vickers K machine guns) for protection against enemy aircraft. The Type II gave up two torpedo tubes, but gained a 6-pounder gun which displaced the twin Oerlikon to the aft deck. This made it more capable of performing the Motor Gun Boat role. Of the 29 built to this design none survives, although a slightly earlier model 60' example has been saved and resides at the Imperial War Museum Duxford annex north east of London.
|Anti Tank Rifles|
|Capital ship main armament|
|Heavy cruiser main armament|
|Secondary armament and|
light cruiser main armament
|Minesweeper, Sloop, Corvette,|
Frigate and Destroyer armament
|Small craft armament|