It just occurred to me that this title may be insensitive. That's OK; I'm insensitive. But I digress. Deer season is about to get under way, and I thought the following might be useful.
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.
This experience has extended itself elsewhere. I've killed whitetails and mule deer as small as 70 pounds and as large as 300 with cartridges as small as the 6mm Remington and as large as the .340 Weatherby. No difference. Deer, of any size, are not hard to kill. There are animals that do require some horsepower, but not these.
If called upon to kill a deer these days, I will choose either a 6.5x55, or a 7mm/08, or if there may be a long shot, a .270. All you have to do is shoot good and the deer will drop.