The

Rheinmetall-Borsig Rheinmetall AG is a German automotive and arms manufacturer, headquartered in Düsseldorf, Germany. Its shares are traded on the Frankfurt stock exchange. History Rheinmetall was founded in 1889. Banker and investor Lorenz Zuckermandel L ...

MK 103 ("MK" - '' Maschinenkanone'') was a German

30 mm caliber 30 mm caliber is a specific size of popular autocannon ammunition. Such ammunition includes NATO standard 30×113mmB and 30×173mm (STANAG 4624), Soviet 30×155mmB, 30×165mm, and 30×210mmB, Yugoslav 30×192mm, Anglo-Swiss 30×170mm, and ...

autocannon An autocannon, automatic cannon or machine cannon is a fully automatic gun that is capable of rapid-firing large-caliber ( or more) armour-piercing, explosive or incendiary shells, as opposed to the smaller-caliber kinetic projectiles (bull ...

that was mounted in German combat aircraft during

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 ...

. Intended to be a dual purpose weapon for anti-tank and air-to-air fighting, it was developed from the

MK 101 MK or mk may refer to: In arts, entertainment and media Fictional characters * Moon Knight, a Marvel Comics superhero * M.K., an ''Into the Badlands (TV series), ''Into the Badlands'' (TV series) character * Mary Katherine "M.K." Bomba, the prot ...

. Compared to the MK 101 it was faster firing, and was originally intended to develop a higher muzzle velocity than the MK 101. Unlike the MK 101, the MK 103 used a belt feed, allowing it to potentially carry a larger ammunition load. The MK 103 used electrically primed rather than percussion-primed ammunition. The operating mechanism differed from the recoil-operated MK 101 in that it used a combination of gas and

recoil operation Recoil operation is an operating mechanism used to implement locked breech, autoloading firearms. Recoil operated firearms use the energy of recoil to cycle the action, as opposed to gas operation or blowback operation using the pressure of the p ...

. After firing, gas pressure served to unlock the breech, while barrel recoil was used to cycle the action (eject spent cartridge and load a fresh one). Because of a combination of lower grade steels and lighter components, the mechanism of the MK 103 was not as strong as the MK 101. To counteract this weakness, HE ammunition with a reduced load of propellant was used, resulting in a loss of about 100 m/s in muzzle velocity compared to the MK 101, but the rate of fire was increased. The MK 103 entered service in 1943 as the main armament of the Hs 129 B-1 ground-attack/tank-destroyer aircraft, mounted on the underside of the fuselage in a conformal

gun pod A gun pod is a detachable pod or pack containing machine guns, autocannons, revolver cannons, or rotary cannons and ancillaries, mounted externally on a vehicle such as a military aircraft which may or may not also have its own guns. Description ...

. The original specification for the MK 103 called for it to fit inside an aircraft's engine mounting (possibly as a ''Motorkanone'', firing through a hollow propeller hub), but it proved to be too large and heavy to fit into small fighters like the

Bf 109 The Messerschmitt Bf 109 is a German World War II fighter aircraft that was, along with the Focke-Wulf Fw 190, the backbone of the Luftwaffe's fighter force. The Bf 109 first saw operational service in 1937 during the Spanish Civil War an ...

. If mounted elsewhere, such as in the wing, the asymmetric force of the cannon's recoil tended to yaw the aircraft's nose to one side. The only known usage of the MK 103 in a ''Motorkanone'' installation was in the Do 335. A modified version with a reduced-profile barrel, the MK 103M, was developed and possibly tested for use as a ''Motorkanone'' cannon on single-engine fighter planes such as the Bf 109K, but probably never saw active service. As a consequence, the MK 103 was largely restricted to the role of an air-to-ground weapon for use against armoured vehicles. Projectile weights for the MK 103 were ) for the HE/M ammunition and ) for APCR ammunition. Armour penetration for APCR / 60° / or / 90° / . Later in the war the MK 103 was also used as a ground-based anti-aircraft (AA) weapon, using single or dual mounts. It was also used as a ''flak'' autocannon in the Flakpanzer IV "Kugelblitz". Developed alongside the MK 103 was the lighter

MK 108 cannon The MK 108 (German: ''Maschinenkanone''—"machine cannon") was a 30 mm caliber autocannon manufactured in Nazi Germany, Germany during World War II by Rheinmetall‑August Borsig, Borsig for use in aircraft. The cannon saw widespread use as an ...

, which had a shorter barrel and used a modified blow-back operating system. It fired the same projectile, using a smaller cartridge case with less propellant, at a relatively low muzzle velocity. The shorter barrel made it more adaptable, so it saw much greater use.

References

*
Archived DeutscheLuftwaffe.de's MK 103 detailed information page
with photos of internal and

mounts-in German {{WWIIGermanAerialWeapons 30 mm artillery Autocannon Aircraft guns Rheinmetall Weapons and ammunition introduced in 1943 World War II aerial warfare