Try a different scope if you can with the same ring/base set up. If it shoots good it is probably your scope. If it doesn't it could be your rings. Some actually are a different size (height wise) even within the same set. Therefore, when you tighten the rings up you actually bend the scope slightly.
I once had a slug gun (12ga Benelli) that would not shoot for spit. When i proved the scope was ok I changed the bases and rings. It somehow became a tack driver (for a slug gun).

Just my .02!