From Wikipedia:
"The N-37 was a powerful, 37 mm (1.46 in) aircraft cannon used by the Soviet Union. It was designed by A.E. Nudelman to replace the wartime Nudelman-Suranov NS-37, entering service in 1946. It was 30% lighter than its predecessor at the cost of a 23% lower muzzle velocity.

The N-37 was a sizable weapon firing a massive (735 g/26 oz HEI-T, 760 g/27 oz AP-T) shell. Its muzzle velocity was still considerable, but its rate of fire was only 400 rounds per minute. The weapon's considerable recoil and waste gases were problematic for turbojet fighter aircraft, as was finding space for the gun and a useful amount of ammunition, but a single shell was often sufficient to destroy a bomber.

The N-37 was used in the MiG-9, MiG-15, MiG-17, and early MiG-19 fighters, the Yakovlev Yak-25, and others. Production lasted through the late 1950s, although it remained in service for many years afterwards.

Specifications

* Type: single-barrel automatic cannon
* Caliber: 37 mm (1.46 in)
* Operation: short recoil
* Length: 2455 mm (100 in)
* Weight (complete): 103 kg (227 lb)
* Rate of fire: 400 rpm
* Muzzle velocity: 690 m/s (2,260 ft/s)
* Projectile weight: 735 g (26 oz)"