I think another factor that is often overlooked is the individual make up of deer. Simply put, some deer are tougher than others. The same way one person may have larger bones, and tougher ligaments, than another, holds true with animals. I am amazed at how quick one deer will expire with a marginal shot, while another goes very far one a perfect one. My rule of thumb is to ALWAYS place my pin on the spot that will give me the best crack at taking out both lungs, and or heart. The equiptment available today is just too good to not strive for this....JMHO