Lest anyone think I am too lazy to try to determine this, my calipers, set on the shoulder of a fired .243 case, show me that I need to lose about 7/8 inches of that 243 chamber. That will remove all the threads from the Winchester barrel plus about 1/8 inch of cylinder. When I cut the new tenon, I'll have about 1/2 inch of cylinder left. I would still be interested in your experience, however. I would hate to go to the trouble if cutting, threading, and chambering and find that I'm leaving a line on the case where the old shoulder used to be.