If you're only shooting 15 feet like you claim then you should be accurate. But that still doesn't mean a headshot is a good option. So you've killed 13 deer. I've killed 89 of 3 species. All in all I've taken 68 species of game on 3 continents and I know no serious hunters that advocate a head shot under normal shooting conditions. None.

Like I said, find a starving elk with its jaw shot off and then come talk to me. Bottom line the chest is a bigger and better target. Always has been and always will be. Somehow I doubt you would be honest on this site and admit it if you did blow a head shot. Funny that the bad shots never get talked about. I hope you get wiser as you get older because the game deserves it and doesn't deserve being left to starve after you do blow the shot and make no mistake, eventually you will.