For about a dozen years, I hunted whitetails in South Carolina every year. Because I was hunting in a private plantation, and because South Carolina has extremely generous bag limits, I could shoot two deer a day for four days. This adds up to a fair number of deer. During that time I carried a number of different rifles, the smallest of which was a .257 Roberts, the largest a 7mm Weatherby Magnum. I could see no difference whatsoever in "killing power" between the various cartridges.