It's about 20% less powerful than the NS37 in the game.
A small comparison of the three big fighter cannons in game:
30mm MK 108 (109's, Me 163, 262, 190A8 Ta 152)
velocity 505 m/s, projectile weight 330g, ROF 10/s, AH damage 11.6
one second burst damage value: 116
37mm M4 (P-39)
velocity 610 m/s, projectile weight 608g, ROF 2.5/s, AH damage 13.2
one second burst damage value: 33
37mm NS-37 (Yak-9t)
velocity 900 m/s, projectile weight 735g, ROF 4/s, AH damage 16.7
one second burst damage value 66.8