Quick possibility - since most bore sighters are using a 1.5" value for height, measure the distance from the center of the bore to the center of your lens in the bell.. If the result is more than 1.5", it's very possible your bases/rings are fine - take the rifle out, shoot it at short range (like 25 yards) and work to adjust the scope to give you approximately 1" low from bullseye.. See if you have any room left then on the scope..
