After discussions with the barrelmaker we agreed that it would be best if I sent come cases that fit the chamber, the fireformed cases, a (dummy) loaded case and my cut off cases to them, and returned the complete rifle.
I got the rifle back quickly with a 1 day turn around in the shop. I couldn't detect or see any changes in chamber dimensions, however I kept one fireformed case to measure against the newly fireformed cases as personal interest, just to see what dimensions had changed. What's important to me is that now now every one of my formed cases, loaded rounds and fireformed loaded cases fit. I couldn't be more pleased with the fitting but I haven't fired it yet; I hope my enthusiasm is not premature.
We're going on a prairie dog hunting trip tomorrow morning, we'll see how it performs.
I'm no machinist but I conclude that the barrelmaker achieved close to the minimum edge of tolerances when they cut the chamber, and the diemaker achieved closer to maximum tolerances when cutting the sizing die. Even though the dies were made by Redding and the barrel maker is unquestionably reliable, (claims "tight" tolerances) they were both "within tolerances" and in this case they were not compatable. It was fixed without fuss, and I don't think more than a thou was taken out of the chamber!
More when I have it.
Shotgun