What size of scope do you have? Are you using low rings? Perhaps try going to medium height rings to give you a little more clearance. I've never experienced this problem with Vanguards, Remingtons, Winchesters, or any other type of bolt action. If your thumb is contacting the scope tube, I wouldn't think it would matter which type of bolt action you were using - all scopes have the same general relationship to the receiver.