RugerR Comments helped.
you look closely at a Ruger scope ring, you will see a bevel on the tightening lug side the mounts on the receiver.
Also the recoil lug needs fitting.
Ruger needs to supply better mounts for their guns. Ruger was no help on this.
Optics Planet and Leather Wood were a help.
Pros: It is the only mount that works good with a M77 and a Aries 390 night scope
Cons: It took a little work to make it fit down tite
This review was written in the old system and had content requirements that are different than reviews written today.