M4 autocannon

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	Weapon: M4 autocannon Type: Autocannon Country of Origin: United States Year Adopted: 1942 Caliber: 37x145mmR Action: Recoil Operated Overall Length (mm): 2270.0 Overall Length (in): 89.37 Weight (kg): 97.00 Weight (pounds): 213.85 Effective Range (m): 2000 m Effective Range (yards): 2187.23

The M4 autocannon was an American 37mm aircraft cannon developed during World War II, based on the design of the earlier M1 cannon and influenced by the German Bordkanone series. It used a long-recoil action, and though originally conceived for anti-aircraft purposes, it found its niche as an offensive aircraft weapon. The M4 fired 37x145mmB rounds, delivering a powerful punch suitable for disabling enemy bombers and light ground vehicles. Its relatively slow rate of fire (around 150 rounds per minute) was a trade-off for its heavy-hitting capability.

The M4 was mounted primarily in aircraft such as the Bell P-39 Airacobra and the P-63 Kingcobra, where it was placed in the nose to take advantage of the cannon's centerline firing. This allowed pilots to precisely aim the weapon, and a well-placed shot could cripple or destroy a target in a single hit. Though somewhat limited by its small ammunition load (typically around 30 to 58 rounds), the M4 served well in the ground attack and bomber interception roles. Its performance was particularly noted in the Soviet Union, where P-39s with the M4 cannon were heavily used under Lend-Lease agreements.

While the exact production numbers of the M4 cannon are difficult to confirm, thousands were manufactured alongside the P-39 and P-63 aircraft during the war. Its impact was most strongly felt on the Eastern Front, where Soviet pilots came to appreciate its destructive power. The M4 was gradually phased out after WWII, as jet aircraft and higher rate-of-fire weapons like the M24 and later rotary cannons became more prominent. Still, it remains notable for being one of the heaviest aircraft cannons mounted in a fighter during the war and for its service legacy in the hands of Allied pilots.