A safety feature incorporated in the design of the trigger mechanism prevented firing the round until the breech-block assembly was in the battery position.

The breech was locked and unlocked by recoil action which brings the operating level guide pins against cams to raise and lower the breechblock.

The springs then drove the lock frame assembly forward to operate the ejector, chamber the round and raise the breech block.

The 37 mm cannon was disliked by pilots for its low muzzle velocity, resulting in more pronounced drop than other contemporary weapons.

It was used as a limited standard aircraft in North Africa campaign and the Pacific theater by the USAAF and Allied air forces.

The more pronounced ballistic trajectory was unfamiliar for American pilots, and the four M4s were replaced with a single 75mm M5 cannon and a pair of .50 caliber heavy machine guns.

The first US jet, the Bell P-59 Airacomet, saw two out of three YP-59s and the single XP-59 armed with twin nose-mounted M10 autocannons, a slightly updated and refined version of the M4.

The M4 37 mm (1.46 in) automatic cannon was mounted on numerous U.S. Navy PT boats as deck guns, beginning with the Solomon Islands campaign.

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 M4 was sometimes employed against soft ground targets on the Eastern Front but was primarily used in air-to-air combat, in which role it was highly effective.