The guns weren't syncronised and the Soviets themselves found out that in order for the guns to be remotely succesfull, they should be syncronized and muzzle breaks should be installed to reduce recoil. In Soviet studies it was found that 52% of the hits with the NS-37 rendered a medium tank out of service, and 73% of hits did the same for a light tank. However, hits were only scored on 43% of combat sorties and the ratio of hits to ammunition spent totalled 3%. To destroy a heavy tank like a Tiger the turret roof or the engine compartment had to be hit from an angle of 45-50 degree. The was something majority of the IL-2 pilots could not do.
Just a sidenote...
IL-2 3Ms (NS-37 armed m3s) were first fielded in the august of '43. Total of 96 NS-37 armed IL-2s made combat sorties during these service tests. The pilots who took part of these service trials stated that the aircraft armed with the NS-37s had worse maneuverability and controllability and that those facts made counterflak maneuvers, attack runs and aiming more difficult. The same pilots thought that despite the high efficiency of the NS-37 an IL-2 armed with them was not superior to the VYs-23 armed aircraft as far as combat cababilities were concerned.
As a result of these unfavourable experiences during these service trials on 12th November '43 the State Defence Commitee ordered the series production of the NS-37 armed IL-2 to be terminated.
(Source: ILJUSIN Il-2, ILYUSHIN IL-2 ATTACK AIRCRAFT by Oleg Rastrenin, ISBN 978-80-87161-02-9)
So it was used in combat on service trials only and the trials proved to be unsuccesful and the production was terminated. When compared to the other planes/loadouts there are in AH, it's IMO pretty clear that the NS-37 loadout for IL-2 is hardly AH-material. Wether Pyro was aware of these facts when he implemeted the loadout for AH I'm not sure.
