The threads depend on when Century made it and whether made from imported parts set with surplus barrels. One way to try to remove it is determine where the weld is, drill it down past the weld and use magnet to get the plug out of the hole. The 2 I did I couldnt see the weld evidence and became frustrated trying to determine where the plug was. Took dremel with cutoff wheel. Scored both sides along length, the area of the break forward of the barrel I cut all the way through along the centerline holes. Took a metal chisel and drove down into the cut splitting the break in half.