about 1944. Starting in late 1940 these were replaced by the very different Mauser MG 151/15 and Mauser MG 151/20 autocannon, respectively of 15mm (early) and 20mm calibre (primary production). References Bibliography Heller, Daniel. Zwischen Unternehmertum, Politik und Überleben. Emil G. Bührle und die Werkzeugmaschinenfabrik Oerlikon, Bührle & Co 1924–1945. Verlag Huber: Frauenfeld 2002. The Machine Gun, History, Evolution, and Development of Manual, Automatic, and Airborne Repeating Weapons. 1951 by George M. Chinn, Lieutenant Colonel USMC. Prepared for the Bureau of Ordnance Department of the Navy. Oerlikon-Contraves Aircraft guns Autocannon World War II weapons 20 mm artillery