I agree with all of what TOF has said, and will reiterate. I use a scraper made from a file to dress the surfaces of the breech plug and tang, 'cause often they are a little sunken in places on the castings. There should be no movement side to side, back and forth, and the barrel should be level with the top of the tang. Today's Hawken breeches are much better than ones from years ago, as far as fit is concerned. A felt pen shows contact much better than inletting black during metal to metal fitting, but I use the Jarrow's black when inletting the unit into the wood. I inlet the barrel into the wood without the plug and tang first, then reassemble them and inlet the breech as a unit with the barrel. I solder the tang to the breech plug and then turn it upside down and sight along the barrel to ensure that the tang is in line with the bore. It often is not and must be bent straight. That makes a big difference to the wrist of the rifle when inletting and shaping.