Red Neck you are correct, but I had rather indicate my chamber in a place the lap hasn't stopped and started.
???
All shanks I've had in from the various makers have a centering cut at the bore that's independant of the lapp. Don't you use a centering rod during setup?
Maybe I'm way off here..
But the shank's cut to length (tenon+shank) and then mounted and squared in the lathe before bore is indicated with the centering rod.. That removes the 'start/stop' area of the lapp..
Even so, let's assume the barrel ordered was a short-shank.. After mount/square - it's easy to take a boring bar and make a 1/8" indent around the bore.. Then re-install the centering rod and double-check the indicator for zero.. Most times it's going to be off .010-.050.. Another 5 mns of adjusting the 4-jaw and you should be at true zero..
To be clear - I'm not in any way questioning you - I was just trying to understand exactly what you meant.. It took me a while - but then, I'm old..
Sorry Butch..