 Developed in 1935 by Rheinmetall-Borsig as a commercial venture as the MG-101 (later designated MK 101, with the "MK" abbreviating the term "Maschinenkanone", as an autocannon), the MK 101 cannon was a 30 mm (1.18 in), long-barreled automatic cannon capable of firing nine different types of 30x184B mm ammunition (ranging from basic high explosive to tungsten-cored armor-piercing rounds).Featuring pneumatic cocking and fired by percussion via an electrical solenoid, the MK 101 was recoil-operated.In operation, the barrel and bolt recoiled 30 mm (1.18 in) to the rear after each shot.