If you take a look at a 6.5 mm bullet, you will see that there is a whole lot of breaking up to be done before there isn' t much left of them. The Rem corelokt 140 gr 6.5 mm bullets are very long, longer than the 168gr .308 BTHP SMK' s I shoot in competition. A long narrow bullet shot at moderate velocities is going to out penetrate a thicker shorter bullet at higher velocities under most circumstances. AN interseting experiment might be to see how your .260 or 7mm-08 will penetrate wet phone books compared to a 30-06 hunting load. I' ve been considering trying that with one of my 6.5 Swedish rifles and my 30-06. I would bet that depending on the bullet designs used, they would perform as well if not better in penetration.

A little anecdote, from what I have read, the Swedish have been using the 6.5x55 (about the equivalent to the .260 REM) for hunting elk or moose for about 100 years. By all accounts its more than adequate, but the hunters must pass an anual marksmanship test in order to purchase their hunting licenses.

A heavier .30 bullet would no doubt give you a bit more margin for error with heavy bone, but then again a .45 bullet would be even better, it just depends on where you draw the line. I feel that bullet construction is more important, a 6.5mm or 7mm partition or x-bullet would be much more appropriate than a .30 corelokt, hollowpoint, or ballistic tip on the bigger game.