MG 151 cannon
The Maschinengewehr (MG) 151 is a belt-fed autocannon for aircraft use, developed in Nazi Germany from 1934 to 1940 and produced by Waffenfabrik Mauser during World War II. It was originally produced in 15.1 mm caliber from 1940, with a 15×96mm cartridge, but due to demand for higher effect against aircraft, especially with the introduction of mine shells for the 20 mm MG-FF/M aircraft cannon, the design was rechambered to 20 mm caliber in 1941, using a newly developed 20×82mm cartridge which traded muzzle velocity for explosive power. The initial 15 mm variant then became known as the MG 151/15, with the new 20 mm variant becoming the MG 151/20.