Remember that the 18- 18 1/2" is from the bolt face, don't cut too short,
something I have done about the bead is to put some masking tape on the barrel where your new bead will be BEFORE you cut the barrel, then mark cente of reciever top and use a streight eage from thet mark to each side
of the front bead still on the barrel and mark the tape at the new point,
small center punch mark at center of the two matks and it will be right on.