If you can just send me the design for the boring bar which is going to cut consistent chambers for me, without the use of a reamer, I'll be happy to give it a look. I spent enough time honing and lapping valve bodies which were bored that I have a little trouble visualising the process. The program produces a virtual product. I want to see the actual result when the chips are produced.
Seriously, if we are to produce a chamber with a body diameter of about .460", at the small end, like a 6BR, we can probably use a 3/8 diameter bar. We'll rough the body with a drill to about.406" then bore to the juncture of neck and shoulder. I think this could be done and be done pretty well. To produce the shoulder angle, the 3/8 bar won't work because it won't have the clearance so we'll have to go to a smaller diameter. No big deal although tool deflection is going to rear it's ugly head. To bore the neck, we can use a larger diameter bar with a small tip so deflection shouldn't be so much of an issue and we may be able to bore a pretty decent neck. Now for the throat. Reamers can cut a throat to within .0001" while producing a good finish and a transition angle which is precise. smooth and free of burrs. Maybe our special bar can do this as well but, given the interrupted cut and all, I kind of doubt it.
In addition, at some point, one or the other of the boring tools is going to dull or lose a tip. When this happens, the machine will go on, blithely, cutting away. The chamber will be ruined and this will be discovered after the barrel is removed from the machine. No big deal really. We can always fix it with a reamer.