Burris Sig rings w/inserts. All you will need within the useable distance of a 6BR and scope.
No more rings marks too.
First thing, shoot the rifle. If you have 30min of elevation left, you can go at least 800yds, most likely 1000yds. How far do you want to go?
Shim a scope AFTER you find out you need it and how much you need. That is why the Burris rings are so good. You can adjust to whatever your rifle/scope/load needs.
Jerry