Sweet Shooter, a perfect sight picture is important in that it's what is desired when firing pin strikes the primer. But nobody hand holds a firearm perfectly still. The best rifle marksmen will hold a rifle slung up in prone under a 3/4 MOA area then try to break their shots inside a 1/2 MOA area.
But while the bullet's going down the barrel and the old physics law of equal and opposite reaction's gonna start moving the rifle's bore axis up, back and sideways. How much it moved while the bullet's in it determines where the muzzle points when the bullet exits. Even with a perfect sight picture for everyshot, the bore axis won't point to the same place for every shot; us humans can't hold perfectly still. . . .unless they're dead and rigor mortis has firmly set in.
Different cheek pressure on the stock's the same as different fore end pressure on the barrel. Neither's good for accuracy.
People have tested their 30 caliber match rifles for accuracy when they're clamped in machine rests and shoot sub 2 inch groups at 600 yards. But the best they can do shooting that stuff slung up in prone and calling all their shots inside a 2 to 3 inch area on target, they don't put all the bullets any tighter grouped than 8 to 10 inches on the average at best; sometimes a lot more. It's all due to how their inconsistant body position causes the rifle recoil for each shot to move the bore/muzzle axis to different places when the bullets exit.
Even handgun front sights are higher above the bore axis than the rear sight; that bore axis moves up from recoil while the bullet goes down the holes it's fired in.
And 50+ caliber double rifles bore axes cross at about 15 yards down range. That way they shoot to point of aim at 100 yards. The rifle moves sideways in recoil before the bullet leaves; left for the left barrel, right for the right one.
US Navy Distinguished Marksman Badge 153
Former US Navy & Palma Rifle Team Member
NRA High Power Master & Long Range High Master
NRA Smallbore Prone Master
Last edited by Bart B.; February 21, 2013 at 08:50 AM.