Purchased a PC 10.5" 500 Magnum. I ran out of adjustment on the rear sight, groups great, just 5" low at 25yds.
Put a Vortex Venom on it, out of vertical adjustment, shot 5" low. Was advised to buy a shim for the sight, i did. Still 3" low...
I've tried bullets from 275-440 grain, 3 different...