37mm M4 Cannon

The M4 cannon (and its derivative, the M10 Cannon) belong to a class of large caliber autocannons that are often capable of critically damaging or destroying an aircraft with a single hit. These cannons are also very accurate once their slow muzzle velocity and trajectory are understood, and effective fire can be laid on larger targets from a kilometer or more. The tradeoff for these huge benefits comes in the form of low rate of fire and limited ammunition capacity. Planes with this weapon have only thirty rounds, with M10 equipped aircraft carrying 58. Given these limitations, these weapons are best employed against larger or unmanuevering targets, fired independently of other weapon systems to enable precise aiming. Single aimed shots are preferred over sustained bursts, as the recoil from firing disrupts the point of aim significantly. Due to the low muzzle velocity additional lead should be applied to targets and drop should be compensated for.

Ammunition Available

 * Link to the belt type.  Describe each belt here.

Found on

 * Linked list of aircraft featuring the weapon system (note whether offensive or defensive armament)

Operational History
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. The weapon, which was built by Colt, entered service in 1942. It was used in the Bell P-39 Airacobra and P-63 Kingcobra. The cannon was disliked by pilots for its drooping trajectory. In a filmed interview, Air Force pilot Chuck Yeager likened it to "throwing a grapefruit".

During World War II the United States supplied the Soviet Air Forces with the M4-equipped P-39 Airacobra and P-63 King Cobra. The U.S did not supply M80 armor-piercing rounds for these Lend-Lease aircraft—instead, the Soviets received 1,232,991 M54 high-explosive rounds. The M4 was sometimes used against soft ground targets but was primarily for air-to-air combat on the Eastern Front at which duty it was highly effective. The Soviets did not use the P-39 for tank-busting. Soviet pilots appreciated the M4's reliability but complained of its low rate of fire (three rounds per second) and small magazine size (30 rounds).