My problem with the .223 for deer hunting is that it is a very light high velocity round that very frequently does not give up its energy in the body of the beast, but passes straight through and continues to be a potential danger for quite a distance. This is great for military use, where your objective is to injure, not kill, as many opposing troops as possible.

I prefer a heavy slower bullet like a .729 that goes up and falls like a mortar. These give up all their energy on impact and knocks the animal over, the shock wave set up then pretty much ensures one shot, one kill.