When I was young, I was told that center fires were O.K. to dry fire and that rim fires were not by experienced men that should have known, so this has always been my normal practice with my own rifles. Others very much disagree. I remember reading Elmer Keith saying that he never let anyone dry fire his guns as he had seen firing pin tips "crystalize" and break off from too much dry firing and I always wondered about that. Currently, I only worry about this on antique rifles that I know it would be difficult to replace the firing pin. On the other rifles, this would be a cheap repair if it ever did happen. Actually, I don't dry fire rifles much anyway.