The MG FF was a drum-fed,

blowback-operated Blowback is a system of operation for self-loading firearms that obtains energy from the motion of the cartridge case as it is pushed to the rear by expanding gas created by the ignition of the propellant charge. Several blowback systems exist ...

, 20 mm aircraft autocannon, developed in 1936 by

Ikaria Werke Berlin Icaria, also spelled Ikaria ( el, Ικαρία), is a Greek island in the Aegean Sea, 10 nautical miles (19 km) southwest of Samos. According to tradition, it derives its name from Icarus, the son of Daedalus in Greek mythology, who was be ...

of Germany. It was a derivative of the Swiss

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 fi ...

F cannon (its ''FF'' suffix indicating ''Flügel Fest'', for a fixed-mount, wing location from the Swiss original), with the Oerlikon FF design itself a development of the Imperial German World War I Becker 20 mm cannon, and was designed to be used in space-limited, fixed mountings such as inside aircraft wings, although it saw use as both an offensive and a defensive weapon, in both fixed and flexible format. It saw widespread use in those roles by the German

Luftwaffe The ''Luftwaffe'' () was the aerial-warfare branch of the German ''Wehrmacht'' before and during World War II. Germany's military air arms during World War I, the ''Luftstreitkräfte'' of the Imperial Army and the '' Marine-Fliegerabtei ...

, particularly during the early stages of

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

, although from 1941 onwards it was gradually replaced by the Mauser firm's 20 mm MG 151/20, which was lighter, and had both a higher rate of fire and muzzle velocity.

Development

MG FF stands for ''Maschinengewehr Flügel Fest'', which translates into "machine gun, wing, fixed"; this reflects the fact that in Luftwaffe practice guns of 20 mm or less were designated as "machine guns" (''maschinengewehr'') as opposed to larger "machine cannons", or autocannons, which were "MK", for ''maschinenkanone''. The "wing, fixed" part reflects the fact that the primary motivation behind its design was to create a 20 mm caliber weapon that was compact and light enough to be mounted in the wings of aircraft, especially fighters. Bf 109E-3 in flight (1940)

Compared to rival designs, such as the

Hispano-Suiza HS.404 The HS.404 is an autocannon originally designed and produced by Spanish/French company Hispano-Suiza in the mid-1930s. It was widely used as an aircraft, naval and land-based weapon by French, British, American and other military services, par ...

– which had been developed from the larger Oerlikon FF S – the MG FF had some disadvantages, such as low rate of fire and low muzzle velocity, as well as limited ammunition storage in its drums. On the other hand, it was much lighter and shorter. Even with its compact size, wing installation on the Messerschmitt Bf 109 and Focke-Wulf Fw 190 fighters was not easy, as the drum required substantial space, and as a consequence the ammunition storage was initially reduced to 60 shells per drum. An ammunition drum of 90-round nominal capacity was developed for the Fw 190 A-5, and retrofitted to some earlier variants. There were also experiments with belt feedings. The MG FF was adapted to fire a new type of high-capacity,

high-explosive An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An expl ...

mine shell A mine shell (from the German term ''Minengeschoß'', "mine shot"), also known as High-Explosive, High-Capacity (HEHC) in British military nomenclature, is a military explosive shell type characterized by thin (usually steel) shell walls and a cor ...

" that featured a projectile with thinner walls that allowed increased explosive charge. This projectile was lighter and thus had a higher muzzle velocity than the previous ammunition; this also entailed that it generated less recoil than earlier projectiles requiring a modification of the recoil mechanism. With this modification it could fire the new mine shell, but accidentally using the heavier MG FF ammo could damage the gun. In the interest of avoiding such errors, the weapon was redesignated the MG FF/M. It was introduced with the Bf 109 E-4 and Bf 110 C-4 in summer 1940. The MG FF fired a 134 g projectile with a muzzle velocity of some 600 m/s and a rate of fire of about 530 rounds per minute. The MG FF/M fired a 90 g HE/M (high explosive mine shell) projectile with a muzzle velocity of c. 700 m/s and a rate of fire of c. 540 rounds per minute. AP, HE and incendiary projectiles were also available (115 to 117 g projectiles, 585 m/s, c. 520 rpm) because the mine-shot was not capable of holding incendiary or tracer parts. There were also different types of high-explosive mine shell fillings with either standard Pentrit A (

PETN Pentaerythritol tetranitrate (PETN), also known as PENT, PENTA, (ПЕНТА, primarily in Russian) TEN, corpent, or penthrite (or, rarely and primarily in German, as nitropenta), is an explosive material. It is the nitrate ester of pentaerythri ...

Aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...

), a mixture called HA 41 (

RDX RDX (abbreviation of "Research Department eXplosive") or hexogen, among other names, is an organic compound with the formula (O2N2CH2)3. It is a white solid without smell or taste, widely used as an explosive. Chemically, it is classified as a ...

powder)(the latter had a 40 percent increased high explosive and incendiary effect).

Operational use

The MG FF and FF/M saw widespread use in fighters such as the Bf 109 E-3 to F-1,

Bf 110 The Messerschmitt Bf 110, often known unofficially as the Me 110,Because it was built before ''Bayerische Flugzeugwerke'' became Messerschmitt AG in July 1938, the Bf 110 was never officially given the designation Me 110. is a twin-engine (Des ...

C to F, and Fw 190 A-1 to A-5. Early variants of the Fw 190 (A-1 to A-5) were typically fitted with an inboard pair of MG 151 and an outboard pair of MG FF/M, although the MG FF/M were sometimes removed in the field in order to save weight. The MG FF/M fed from a 60-round drum that required an underwing bulge to fit within the wing (90 rounds in the A-5). From the A-6 onward, the MG FF/M were replaced by a pair of MG 151/20 feeding from 125 round belts, or deleted altogether. The cannon was also fitted to bombers such as the

Do 217 The Dornier Do 217 was a bomber used by the German '' Luftwaffe'' during World War II as a more powerful development of the Dornier Do 17, known as the ''Fliegender Bleistift'' (German: "flying pencil"). Designed in 1937 and 1938 as a heavy bomb ...

Ju 88 The Junkers Ju 88 is a German World War II ''Luftwaffe'' twin-engined multirole combat aircraft. Junkers Aircraft and Motor Works (JFM) designed the plane in the mid-1930s as a so-called '' Schnellbomber'' ("fast bomber") that would be too fast ...

He 111 The Heinkel He 111 is a German airliner and bomber designed by Siegfried and Walter Günter at Heinkel Flugzeugwerke in 1934. Through development, it was described as a "wolf in sheep's clothing". Due to restrictions placed on Germany after th ...

, Do 17, as well as many other aircraft, either as aerial defense, or more often for anti-ship and defensive fire suppression. Although the MG FF was often replaced with the 20 mm MG 151/20 from 1941 onwards, it saw a comeback in 1943 as the primary

Schräge Musik ''Schräge Musik'', which may also be spelled ''Schraege Musik'', was a common name for the fitting of an upward-firing autocannon or machine gun, to an interceptor aircraft, such as a night fighter. The term was introduced by the German ''L ...

gun in the

(and other) night fighters, as it fit perfectly into the rear cockpit, and muzzle velocity was less important in this application (there were also stocks of surplus guns and ammunition to be used up).

Technical data

L.Dv. 4000/10 *Weight: 26.3 kg *Length: 1.37 m *Muzzle velocity: ** (MG FF with HE), ** (MG FF/M with AP or HE), ** (MG FF/M with API), ** (MG FF/M with (HE(M)), ** (MG FF/M with (HE(M)), ** (MG FF/M with (HE(M)) *Rate of fire: ** 530 rpm (MG FF with HE), ** 520 rpm (MG FF/M with AP or HE), ** 540 rpm (MG FF/M with HE(M)) *Round types: ** armor-piercing (AP) (MG FF/M), ** armor-piercing incendiary (API) (MG FF/M), ** armor-piercing high-explosive (APHE) (MG FF/M), ** high-explosive (HE), all with or without tracer (MG FF, MG FF/M), ** high-explosive incendiary (HEI), all with or without tracer (MG FF/M), ** high-explosive mine shell (HE(M)) (only MG FF/M), ** incendiary (I), all with or without tracer (MG FF/M)

Ammunition specifications

Notes and references

External links