The way it was explained to me when I was first starting out (6 years ago) was, behind the front shoulder you have a paper plate sized area where all the Vital Organs for a deer are. If you aim just behind the shoulder you are apt to get a double lung, a heart shot, or both in the same shot. Every deer Ive taken Ive shot behind the shoulder and each and every deer has dropped on the spot, Ive never had to track a single deer. If you try to shoot a buck in the head, your liable to mess up the " Rack" or ruin any chance of mounting the Trophy. So, personally I aim just behind the front shoulder