I recently finished my 6.5x284 using a left handed Montana Rifle Co action and a 26" Krieger (1:8.5 twist) barrel. I put a Farrel 20 MOA scopemount on it and it shoots 15" high at 100 yards with the scope adjusted all the way down. I can't change to a 10 MOA mount because the rig is left handed.

What are the adjustable rings?

Burris Signature rings use plastic inserts. They also sell inserts with different offsets. This would allow you
to change the angle of the scope without binding the scope tube. The inserts are rounded and the inside of the rings are rounded allowing the scope to sit at an angle in the rings without binding. This eliminates the need
for ring lapping.

I have used these burris ring inserts and they work great. I have them installed in 2 rifles right now.

Hoeram

You may have a scope with not enough adjustment for a 20moa cant base.