This is a VERY NICE example of a 100% INERT WW2 German Wehrmacht/Luftwaffe 30mm MK103 Steel Shell, as used by the Hs129 Tank Destroyer Aircraft!
The Rheinmetall-Borsig MK 103 (“MK” – Maschinenkanone) was a German 30 mm caliber autocannon that was mounted in German combat aircraft during World War II. Intended to be a dual purpose weapon for anti-tank and air-to-air fighting, it was developed from the MK 101. 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. 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.
Made of solid steel, this is a FANTASTIC piece of history! Completely inert, there are some slight wear and marks, however it remains VERY SOLID with various marking throughout. Some corrosion and damage as you can see in the photos. This specific example was filled with cement (or similar). Would make a EXCELLENT addition to any collection or display!