.54 or better yet .58!!!!! "walk tall and throw a BIG ROCK!!" If you have hunted very long then you know a Whitetail is a STRONG WILLED ANIMAL!! I have put 180 gr 30-06 bullets right in the kill zone and have seen them run for quite a ways, not always but have seen it. So the way I figure it, I want the biggest round ball I can get to pack a good WALLOP!! YRMV!
"I prefer dangerous freedom over peaceful slavery."
- Thomas Jefferson