Personally, I have taken deer with .45, .50, and .54. The .45 took a 5 X 5 mule deer with one shot. Several whitetails have fallen to the .50 at distances to 75 yards, the last one dropping in its tracks. But that all said, the most impressive kill on a whitetail came at the hands of my .54, and when it hit him, it knocked him over backwards, as he reared at the shot. That ball never came out and he never moved after plummeting backward. They are all good, but you have to hit them in the right place. Caliber is not a remedy for a bad shot.