It was designed for BP , larger clearance for fouling . Modern copies run .004-.006 cylinder gaps for C&B . Up to .008 isn't unusual . The head space is a greater concern and the cylinder can be shimmed to get the endplay travel out and headspace down . As long as the cylinder and barrel line up it should be ok . As a rule a barrel set back doesn't seriously damage value . If parts are replaced keep the OM parts with it .