Lots of variables to consider...
#1) Consistancy of shooter (ability), and not just on a target, but with a live deer in front of you (it's called buck fever).
#2) How far is the shot? I've shot Does between the eyes @ 75 yards (never lost one), I personaly wouldn't consider this shot over 100-125 yards.
#3) What is the deer behavior? Relaxed or jittery.
#4) Windage?
Etc. etc. etc.

Keep in mind as an example, an Army or Marine infantry specialist doesn't make him/her a snipper. Snippers are specifically trained experts.