Wow !!! what a load of crap.
The First thing to do is start with a "STRAIGHT" barrel bore. any good smith can determine this befor he even starts the barrel work.
The next thing to do is set the barrel bore in line with the center of the lathe spindle. then If the barrel has runout, it is on the outside where it can be fixed or rejected and sent back.
With the proper sized bushing/pilot and a proper setup the chamber will be straight and true and be an exact duplicate of the reamer.
As to the same methods of the 1800's tooling, process, and equipment has greatly improved and the evidence of improved accuracy is the results.
Adding another component/threaded connection to the process in the most critical area doesn't make sense and only adds more dimensional error and also makes the area that handles the most pressure weaker and more vulnerable to failure. also with thread clearance (Required to assemble)
expansion in this area will lead to excessive case expansion and bolt lift with loads that normal methods would handle. besides, who would want a seam in the chamber area !
Sorry, I just think that It is a very bad idea and would never buy into this process.
Good "Straight barrels" good barrel set up, and quality tooling plus a good smith would/should never run into the problems he describes. also if this were good we could have barrels in sections that could be screwed together to get different barrel lengths like some cleaning rods.
J E CUSTOM