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 turbojetfighter 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.
N-37 with 1950mm long barrel (had no muzzle brake)
improved N-37L developed during the late 1950s for the Yak-27 reconnaissance aircraft. The NN-37 differed from the N-37L in having a pneumatic counter-recoil accelerator, therefore achieving a rate of fire of 600-700rpm. The ammunition feed mechanism was redesigned as well on this version.