I have to agree with Matt except for one issue. Find the distance that you can shoot all your arrows into an area the size of your intended quarry and then for hunting divide that by two. Because when the adrenalin is pumping, the knees are a knockin, the game is moving, the brain goes bananas.
I can easily shoot 6" groups at 60 yards under target conditions. My absolute max for deer sized game is 35 yards. That's just my ethical standards.