M4 autocannon

Common card · No. 250760

The 37 mm Automatic Gun, M4, known as the T9 during development, was a 37 mm (1.46 in) recoil-operated autocannon designed by Browning Arms Company and entered service in 1942. The M4 and its variants would primarily be manufactured by Colt's Manufacturing Company and Oldsmobile (under-contract by Colt) and is therefore sometimes referred to as the "Colt M4" or "Oldsmobile M4." It was primarily mounted in the Bell P-39 Airacobra and P-63 Kingcobra, with the US Navy also using it on many PT boats.

Read on Wikipedia