Yep. Had this discussion before.
7.62 x 39 AK type
7.62 x 51 NATO
7.62 x 54 .308
7.62 x 63 30.06
Note: The .308 round is rated at a higher pressure than the 7.62 NATO so even though the will chamber in most rifles interchangeably care should be used when using .308 in an older rifle chambered for the NATO round.
I have a Ruger Mini-30 which shoots the same 7.62x39 ammo as the AK. Its accuracy is pretty disappointing to me. Can any of you make a comparison of the two, touching on reliability, cost,ease of maintenance, etc, as well as accuracy? I bought the Mini-30 as a hedge investment before the 2000 election - - maybe it's time to look over the portfolio again.