When you get into the discussion about what caliber is big enough for deer hunting, the first thing you need to do is check your state's regulations. That caliber may not be legal in your state. As to whether it will kill a deer, there is no question that it CAN kill a deer IF everything is exactly right (close enough, angle, standing still, no wind, good hit, etc.). Most people want something with a little more authority, that is to say a caliber that will kill a deer when things don't go exactly right. My personal belief is that in the unfortunate situation when a wounded deer might run off (especially if it is not recovered) I want to know that I did everything I could to make a clean, humane kill. If you want to use the AR15 just for the fun of it, I would take a hard look at your motives for hunting in the first place. The game animal is just too great to treat disrespectfully. On the other hand, lots of people use guns that are way too big for deer, but dead is dead, and the deer that are hit with these big bullets don't go very far!
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