Not all 7.62 x39's are the same either.
Do you have some info on that? I know that the .223Rem was standardized by
SAAMI for civilian use, whereas the 5.56x45 round was standardized by NATO for the militaries of member nations.
As far as I am aware, there was only one standard for the 7.62x39.
Also, I'm only speaking of dimensions, not different types of bullets like HP, FMJ, TMJ, BT, tracer, etc.