If every time is dead on with the first shot ,then you let the barrel cool ,clean it and are still dead on after a couple of times you will know if its you or that your gun just don't shoot with a clean barrel the same as a dirty barrel. I have friends that always shoot what they call fouling shots just before they get serious on the range .I doubt very much that the heat from one shot will distort the shooting pattern of your rifle 1 1/2" @ 50 yards .