They are a standard thread 3/8-16, however, I am uncertain of the diameter inside the butt cap, the head of a standard bolt may need to be turned down to fit.
Atlas sell these bolts andthey come with a Allen Screw to hold the bumper on.
i HAVE THE ORIGONALS IN THE DRAWER FOR YOU MY FRIEND. i JUST BOUGHT 6 R-SERIES FRONTS,COCO BOLO WITH 1 BLK VEENER.AND BUTT PIECES. i HAVE PLANS FOR 2 CUES- ?? MARK
And thanks to everyone else that posted a reply, I appreciate the help as always.
I have 2 Schons, one I bought used and it came with no weight bolt. If I happen to sell that one, I'd like it to be original and complete for the buyer.