Oerlikon 20 mm cannon
The Oerlikon 20 mm cannon is a series of autocannons based on an original German Becker Type M2 20 mm cannon design that appeared very early in World War I. Widely produced by Oerlikon Contraves and by others, its various models saw service with both Allied and Axis forces during World War II. Versions of the cannon were still in use in 2026. == API blowback-operated models == === History === ==== Origins ==== During World War I, German industrialist Reinhold Becker developed a 20 mm caliber cannon, known now as the 20 mm Becker using the advanced primer ignition blowback (API blowback) method of operation.