I think the lungs are the best overall target, one might get a piece of the heart as well, I have taken a few close head shots when I had good eyes and a rifle I knew very well, where ever you feel is the best spot getting as close as possible is the key to reducing error,even if it means letting some Deer walk, think archery and few Deer will be lost. PRB would be the only choice of projectile I would consider, if conditions for whatever reason made this an unsuitable projectile I would pass the shot or go back to centerfire hunting, anyplace that has archery hunts will produce opportunities for the PRB and some serious traditional hunting.