I have a receiver mount plate that bolts to the sides of the receiver and if I shim the back, I don't think the holes will line up to bolt it on. The rings are not on the bell taper of the scope either. I can try switching rings, but I'd like to know it's bore sighted because I won't be able to sight it in for a while and don't have time to start from square one if it doesn't work after switching rings. As Rosana Rosana Dana used to say, "It's always something!"