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Count clicks from one stop to the other, then put it in the middle. If there's 100 clicks from all the way left to all the way right, count 50 from one end and put it there. Hopefully it's somewhat close to where you want to be when it comes time to bore sight it.
Op it sounds like you may have a bad ring or a twisted base. You could lap your rings with some valve grinding compound and a metal pipe to match your scope size. I'd bet there are plenty of videos out there on how to....