The M4 Automatic Gun is an American 37mm anti-aircraft autocannon employed during World War II, primarily as main armament of the Bell P-39N Airacobra. Designed and produced by John Moses Browning various manufacturers, including the famous Browning Arms Company, it was a versatile and reliable autocannon known for its effectiveness against both aerial and ground targets. Its accuracy, rapid fire rate and firepower contributed to its success in defending against enemy aircraft, and it was mounted on various vehicles, as well as utilized as a naval anti-aircraft gun.