Here's a trick i learned from a buddy that custom builds 50BMG rifles from the ground up. Use a dab of nail polish on the bottom of the rings. Let the polish get a bit tacky before setting the scope in the rings. This guy knows his stuff, i've been using this trick with all of my magnum rifles and it works.
If you ever want to take the scope off that particular rifle, the polish comes right off the scope or bottom half of the rings. It leaves no mark.