I actually have a Bartlien 6BR barrel that I have to shim the rear of the scope ring clamp to get it near zeroed for windage. Other than that, the barrel shoots great.
I used a piece of beer can folded twice and pounded flat. Fits perfectly under the ring clamp and does its job. Scope rail is part of the action and I’ve not had this issue using same scope and action with previous barrel.
It’s about a 6 mil adjustment. Never seen it before, but my redneck fix works like a charm.
Sometimes stuff happens, so use your head and adapt accordingly. But first take it to the range and barrel sight it so that you know what the problem is. That is, after you verify that the scope mount isn’t off somehow or mounted incorrectly.