I've never done it. I just mounted a new set of Leupold rings, they have a very fine kinda cross hatching inside. If I lapped them, that surface would be altered forever. There is a very thin, transparent material called Ring True tape. You can use this to take up slack in a ring. Or to get a better grip on a tube that wants to get and stay loose. Or protect your valuable scope from ring scratching to the tube. I don't go all anal about scope mounting and I haven't ruined or wrecked one yet, never had one fall off.