In re-barreling a rifle, how do you get the iron sights to line up? Threads are not always the exact length to come out correctly. When I hand screw the barrel in, it stops about a 1/16 turn too far. When torqued it will go farther and I am wondering how you deal with this. This is one job I am going to have a professional do, but I am curious about how it is done. Thanks, ahead of time. Grant.