Mikey,
I understand your concern with a comparison of any load in .30-06 to any load in 7.62 x 39. Maybe I just didn't clarify what I meant.
Yes, the .30-06 generates a heap more velocity than the 7.62. That velocity, however, begins to diminish the moment the bullet leaves the barrel. And the .30-06 load I was referring to is the Rem 125 grain pointed soft point (p. 484 column 1, item #7, Shooter's Bible, 2003 Ed.) At 200 yards DOWN RANGE, according to the data, the velocity has diminished to 2447 fps.
OUT OF THE MUZZLE of the 7.62, the Rem 123 grain pointed soft point (essentially the same bullet minus 2 grains) load pushes the bullet at a velocity of 2365 fps. Not exactly the same mass and velocity, but very close for comparison sake. We could go down range a bit more, say 27 yards or so, with the .30-06 bullet and we would have virtually the same mass bullet at the same velocity.
As a matter of physics, these two speeding bullets would have virtually the same momentum and energy (slightly less of course for the 123 grain bullet, but only by a few ft/lbs). Thus they would have virtually the same effect when striking a game animal. That was the point I was trying to make - not that they would be the same energy at the same distances. The 7.62 lags behind the .30-06 in this example by by about 230 yards in terms of energy. So, a deer standing 30 yards away would get hit by the 7.62 bullet with the same force as if it were standing 260 yards away when struck by the .30-06 bullet.
Anyway, we agree that the killing energy of the 7.62 on whitetails is pretty much limited to around the 150 yards or less range, which was the essence of all the ballistic comparisons anyway. I do appreciate your feedback.