Oddities in Ballistics & Not Just Armor Pen

Okay so don't get me wrong, I love the realistic health system and how you can only really die from getting hit in the vitals, or losing all your blood etc.

But sometimes I feel as if wounds are not applying right. (Let alone through armor- that's another story.)

I shoot someone in the arm etc with idk, 9x19 Hollow Point. Light wound.

I shoot someone in the arm etc with 7.62x39 Hollow Point. Light wound.

I'm not a gun expert to say the least, but I know for a fact 7.62x39 HP isn't going to be a 'light wound' it will be heavy at worst and a medium at best.

On to that point, I have never once seen a heavy wound. It's always mediums or lights- that happen to be fatal. Hell, I shot someone in the chest with 7.62x39 US (Subsonic tungsten core round) and it only causes a 'light wound' and somehow doesn't even damage organs.