If seventy percent of the bullet's energy is expended in the hillside behind the animal, I doubt there is much performance difference between an 06 with a 180 or a 260 with a 100.
But when one uses a bullet which delivers most of the available energy to the target, well in my meager experience the game reacts a lot differently to a larger cartridge. At least when the game is deer. I have not killed enough of anything else to make any valid comparisons.
I can state with firm conviction that a deer hit in the vital liver-heart-lung region gets real sick, real fast when the bullet is a 30 cal 165 bt at medium velocity. I can not say the same for the deer I have shot with smaller cartridges such as the 7x57 or 22-250. The deer died quickly, and were recovered easily with the smaller cartridges, but there certainly was not the same visible reaction to the shot.
Instead I would compare the reaction of the deer to the smaller calibers to the reaction of the elk I killed with the 06 and 165's. The elk fell over dead and was fully bled out within forty yards, but still it showed no reaction at the shot. If I had not been so confident in the rifle and my prone position, I would have sworn I had missed cleanly with both heart shots.
