MG 151 cannon

MG 151/15
MG 151/20
Type	Aircraft Cannon
Place of origin	Nazi Germany
Service history
Wars	World War II
Production history
Manufacturer	Waffenfabrik Mauser AG
Specifications
Weight	42.7 kg
Cartridge	15×96mm cartridge
Caliber	15 mm
Rate of fire	680 to 740 rpm
Muzzle velocity	850 m/s

MG 151/20
Type	Aircraft Cannon
Place of origin	Nazi Germany
Service history
Used by	See users
Wars	World War II Algerian War Rhodesian Bush War
Production history
Manufacturer	Waffenfabrik Mauser AG
Specifications
Weight	42 kg
Length	1.76 meters
Cartridge	20×82mm cartridge
Caliber	20 mm
Rate of fire	600–750 rpm
Muzzle velocity	700 metres per second (2,300 ft/s) to 785 metres per second (2,580 ft/s)

The MG 151 (MG 151/15) was a 15 mm aircraft-mounted autocannon produced by Waffenfabrik Mauser during World War II. Its 20mm variant, the 20 mm MG 151/20 cannon, was widely used on German Luftwaffe fighters, night fighters, fighter-bombers, bombers and ground-attack aircraft. Salvaged guns saw post-war use by other nations.

Development and wartime history (MG 151/20)

The pre-war German doctrine for arming single-engine fighter aircraft mirrored that of the French. This doctrine favored a powerful autocannon mounted between the cylinder blocks of a V engine and firing through the propeller hub, known as a moteur-canon in French (from its first use with the Hispano-Suiza HS.8C engine in World War I, on the SPAD S.XII) and by the cognate Motorkanone in German by the 1930s. The weapon preferred by the French in this role was the most powerful 20mm Oerlikon of the time, namely the FFS model, but this proved too big for German engines. Mauser was tasked to develop a gun that would fit, with a minimum sacrifice in performance. (As a stop-gap measure, the MG FF cannon was developed and put in widespread use, but its performance was lackluster.)

Production of the MG 151 in its original 15 mm calibre format began in 1940. After combat evaluation of the 15 mm cartridge as the main armament of early Messerschmitt Bf 109F-2 fighters, the cannon was redesigned as the 20 mm MG 151/20 in 1941 to fire a 20 mm cartridge. Combat experience showed that a more powerful explosive shell was preferable to a higher projectile velocity. The MG 151/20 cartridge was created by expanding the neck of the cartridge to hold the larger explosive shell used in the MG FF cannon, and shortening the length of the cartridge case holding the longer 20 mm shell to match the overall length of the original 15 mm cartridge. These measures simplified conversion of the 15 mm to the 20 mm MG 151/20 simply by changing the barrel and making other small modifications. A disadvantage of the simplified conversion was reduction of projectile muzzle velocity from 850 metres per second (2,800 ft/s) for the 15 mm shell to 700 metres per second (2,300 ft/s) for the larger and heavier 20 mm shell. With an AP projectile the new 20mm cartridge could only penetrate around 10-12mm of armor at 300m and at 60 degrees, compared to 18mm penetration for its 15mm predecessor in the same conditions, but this was not seen as a significant limitation. The 20 mm version thus became the standard inboard cannon for the Bf 109F-4 series onwards. The 20 mm MG 151/20 offered more predictable trajectory, longer range and higher impact velocity than the 580 metres per second (1,900 ft/s) cartridge of the earlier MG FF cannon. The MG FF was retained for flexible, wing and upward firing Schräge Musik mounts to the end of the war.

The German preference for explosion rather than armor penetration was taken further with the development of the Minengeschoß ammunition, first introduced for the MG FF (in the Bf 109 E-4), and later introduced for the MG 151/20 as well. Even this improvement in explosive power turned out to be unsatisfactory against the four-engine bombers that German fighters were up against in the second part of the war. By German calculations, it took about 15-20 hits with the MG 151/20 ordnance to down a heavy bomber, but this was reduced to just 3-4 hits for a 30 mm shell, from the shattering effects of the hexogen explosive in the shells used for both the long-barreled MK 103 and shorter barreled MK 108 cannon. (Only 4-5 hits with 20 mm calibre ordnance were needed for frontal attacks, even on B-17s, but such attacks were difficult to pull off.) The 30 mm MK 108 cannon thus replaced the MG 151/20 as the standard, engine-mount Motorkanone center-line armament starting with the Bf 109 K-4, and was also retrofitted to some of the G-series.

Eight hundred MG 151/20 exported to Japan aboard the Italian submarine Cappellini in August 1943 were used to equip 388 Japanese Ki-61-I Hei fighters. The 20 mm MG 151/20 was also fitted on the Macchi C.205, the Fiat G.55 and Reggiane Re.2005 of the Regia Aeronautica and IAR 81C of the Romanian Royal Air Force.

Postwar Use

Two MG 151/20 cannon fitted to a Finnish TorKK MG-151 2 anti-aircraft mounting. Cannons of Torp museum (2011)

After World War 2, numbers of ex-Luftwaffe MG 151/20 cannon were removed from inventory and from scrapped aircraft and used by various nations in their own aircraft. The French Air Force and French Army aviation arm (ALAT) utilized MG 151/20 cannon as both fixed and flexible armament in various aircraft, including helicopters. The FAF and ALAT jointly developed a rubber-insulated flexible mount for the MG 151/20 for use as a door gun, which was later used in combat in Algeria aboard several FAF/ALAT H-21C assault transport helicopters and on HSS-1 Pirate gunship helicopters. French Matra MG 151 20mm cannons were used by Portugal and Rhodesia fitted to their Alouette III helicopters, while Denel designed its own variant for the South African Air Force.

Users

• Germany
• Finland
• France
• Italian Social Republic
• Empire of Japan
• Portugal
• Romania
• Southern Rhodesia
• South Africa

MG 151 specifications

• Type: single-barrel automatic cannon
• Caliber: 15×96mm
• Operation: Recoil-operated; short recoil
• Length: 1916 mm
• Barrel length: 1254 mm
• Rifling: 8 grooves, right hand twist, 1 turn in 16"
• Weight (complete): 38.1 kg (84 lb)
• Rate of fire: 740 rpm
• Effective range: 1000 m
• Muzzle velocity: 850 m/s (AP-T); 960 m/s (HE-T, HEI-T); 1030 m/s AP(WC)
• Projectile types:
  • AP-T weighting 72 g
  • HE weighting 57 g. HE filler: 2.8 g
  • AP(WC) weighting 52 g

MG 151/20 specifications

Two versions of the 20 mm MG 151 were built. Early guns used a percussion priming system, and later E-models used electrical priming. Some rounds were available with a timer self-destruct and/or tracer (or glowtracer). There were also different types of high-explosive shell fillings with either standard PETN, a mixture called HA41 (RDX and aluminium), and a compressed version where more explosives were compressed into same space using large pressures (XM).

• Type: single-barrel automatic cannon
• Caliber: 20×82mm
• Operation: Recoil-operated; short recoil
• Length: 1766 mm
• Barrel length: 1104 mm/55 calibers
• Rifling: 1 turn in 23 calibers
• Weight (complete): 42.7 kg
• Rate of fire: 750 rpm
• Effective range:800 m
• Muzzle velocity: 805 m/s (M-Geschoss); 705 m/s (HE-T, AP)
• Round types:

Ammunition specifications

German Designation	US Abbreviation	Projectile Weight [g]	Bursting charge [g]	Muzzle Velocity [m/s]	Description
Brandsprenggranatpatrone 151 mit L'spur ohne Zerleger	HEI-T	113	2.3 g HE (PETN) + 2.1 g incendiary (Elektron)	705	Nose fuze, tracer, no self-destruct
Brandgranatpatrone 151	incendiary	117	6.6 to 7.3 g incendiary (BaNO3+Al+Mg)	?	Nose fuze
Minengeschosspatrone 151 ohne L'Spur	HE	95	18.6 g HE (PETN)	805	Nose fuze, no tracer
Panzergranatpatrone 151 mit L'spur ohne Zerleger	AP-T	117	none (bakelite filling in cavity)	705	No fuze, tracer, no self-destruct. Penetration 13mm steel at 60-degree impact, 100m range.
Panzersprenggranatpatrone 151	APHE	115	4 g HE (PETN)	?	Detonation after 5mm steel penetration.
Panzerbrandgranatpatrone (Phosphor) 151 ohne Zerleger	API	115	3.6 g incendiary (WP)	720	No fuze, no self-destruct. Penetration 3 to 15mm of steel.
Panzerbrandgranatpatrone (Elektron) 151 ohne Zerleger	API	117	6.2 g incendiary (Elektron)	695	Optimized for strafing unarmoured ships. No self-destruct. Penetration 15 mm of steel at 75-degree impact angle, 100 m range. Fuze functions after 4 mm steel penetration.

US derivative

In the late 1940s the US Army reverse engineered the MG151 in order to adapt it to fire .60 caliber rounds; these had been developed for use in an anti-tank rifle. Around 300 of these T17 guns were built. However none saw service despite the availability of 6 million rounds of .60 caliber ammunition. Almost one million rounds were fired during the T17 testing program. The main US version produced, the T17E3, was made by Frigidaire. Further refinements led to the T39 and T51 versions, but these also did not enter service.

See also

• WW2 Luftwaffe aircraft weapons
• MK 108 30 mm cannon

External links

• Type 151 20mm Cannon
• GA 1 20mm Cannon
• WWII era US Military report on the weapons
• External Image
• Prinz Eugen site containing information
• Aircraft of the Luftwaffe - Gun placements