Range trip today after a complete cleaning of the breechplug with solvent and a drill bit. The blowback was much less then before. Not as good as the brand new plug, but workable. I still need to get another new plug to compare.
I also switched to new MMP sabotsfrom the factory Shock wave sabots. Much better accuracy with no other changes. Both the HPH12 and 24's shot about the same and not much difference in loading difficulty.
I am now getting a consistant flyer that is 1-2 inches high from the rest of the group. Two shots touching and then the flyer. I had three different 3 shot group and all had the same problem. This was with weighed charges of 777, 250 and 200 Shockwave and it wasn't the same shot number in the group. No variations in loading, swabbing, or bag placement.
Any thoughts on what might be causing this?

Also, I had to shim the Weaver base to get enough elevation. Do you think switching to a Warne steel base would help with this?