Hello Jimmy B !
Mine is not counter bored. I thought it probably was after trying my 'Poor Mans Muzzle Gage' on it the first time. But after a quick look... no such thing. Look over this post about mine:
https://www.milsurps.com/showthread.php?t=61219
Good to hear from you.... hope you, Terry and the boys down there are doing well.
Charlie-Painter777