I think we are victims of a misconception about bullet damage to the body.
With round nose, non-expanding, non-tumbling bullets nearly all damage done to the body is small permanent crush cavity, which is mostly affected by bullet caliber. Of course temporary stretch cavity is going to be bigger in case of faster 7,62 rounds, but most studies of this subject (from what I remember) indicated, that temporary stretching of the tissue doesn't really make any difference.
If penetration of nagant revolver bullet exceedes 14 inches of body tissue, I don't really think it should be much less deadly than bullet from TT or even Ppsz. I mean, bullet from PPsh is going to retain more energy when exiting the body, but not really dumping some substantially bigger amount in the tissue.
Of course TT or Ppsh are going to be much better at penetrating all kinds of cover and helmets (which IMO should stop nagant rounds at greater angles/distance) or at killing stupid germans standing in a row. Other than that - it's just going to pierce the same small diameter hole in the body, in most cases probably creating exit wound.
BTW I really hope that 9mm will be more deadly than 7.62 tokarev, since it's bigger and less prone (a bit less probably) to getting deflected by bones but much worse at penetrating cover and helmets (in case of helmets - shots from both 9mm and 7.62 should pierce them at under 40-50m, unless the angle is really big).
BTW2: I have an idea about nagant suppressor "effectivenes".
We all know that suppressors don't work like in hollywood movies. They just make something super-loud less loud, but loud nonetheless. However we're playing as soldiers in the middle of the battle. We're firing unsuppressed weapons indoors and outdoors in narrow streets. Nades are exploding all around us. Artillery shells are exploding here and there. In the middle of such madness our ability to hear would be GREATLY impaired thanks to all this extreme noise and stress (auditory exclusion) and so suppressed shot may be unnoticed from much closer distance than in normal circumstances. The game developers don't want this to happen (playing as half-deaf most of the time isn't that fun) so they're probably going to make Nagant more silent.
It won't be unrealistic. Our ability to hear everything else during the battle is unrealistic. Not being able to hear shot from nagant with suppressor 1 floor above is actually THE realistic part. It'll just contrast with the unrealistically clear sounds of the battlefield.
I'm all against suppressors in this game, but if they are in, I'm not going to cry.