Make sure you have the correct bases. Just because the holes line
up doesn't mean the base is flush to the receiver. Also, some rifles (ruger)
have differents heights of rings from the front to the back. I have
seen an attempt of this- not pretty.
Another problem- the lengths of base screws vary and holes are often
drilled all the way through- thus the screw may touch the bolt.
I have also seen dovetail mounts that are cut differently
where certain recievers need a sharper cut to fit properly on.22's.
Another mistake that could be made is tightening a ring where the objective widens out. Just on the edge be careful. Cheers