It's 100/80/60 pen for 0-60 distance and 80 damage per shot. Truthfully it is considered a terrible AT gun that is really a last ditch gun.
60/300 [Tiger has 300 armor] is 20% pen of the time but it can't compare to a ZiS which has 180/300 at that distance and full 160 dmg per shot even with ~58% the fire rate. Effective dps would be about 3x M-42 on avg vs a Tiger. Which basically means a Tiger will eat the M-42 gun crew alive.
So the M-42 base penetration was buffed to 140/100/80 bumped up to 182/130/104 with vet and an additional 20% bonus pen with essentially the first 2 shots out of cammo. Just to keep your books up to date.
That said, with anything heavier than a panzer 4, the M-42 is only a small threat even with the first strike bonus unless you expose your rear armor.
Granted, a skilled player though can utilize the cammo to get the M-42 into unexpected positions.