I have a CVA Optima Pro muzzleloader and put a Leupold Vari-X 3x9 scope on it with Millet bases and rings. I am using the long rings for hammer clearence. I am shooting 1 inch low at 30 yards and the scope will not adjust up any more. Is there a cheap fix for this? Somoene suggested a shim. Please explain any fixes.

Otherwise, after bore lapping using JB paste, using 100 grains 777 with a 260 grain nosler partion HP and MMP sabots, this thing is a tack driver at 30 yards so far and is nice and easy to load.