Actually, the problem is that you know when the rifle is about to go off, and the flinch is involuntary.

I was always taught that you slap the trigger on a shotgun, and you slowly squeeze the trigger on a rifle. Everyone I' ve seen who flinches has always pulled the trigger fast. Slowly squeeze the trigger, and since you basically know when the trigger trips on your gun, concentrate on becoming very steady and on target just before it trips. You will not know exactly when it will fire, so you won' t flinch. Hope this helps and good luck this season!

Mark
http://www.buckhuntersecrets.com