Thanks for all the info all of you. I am working on a argon atmosphere solution. I thought of the iron pipe thing that was in the article submitted by CMWill. The problem is the carbonization caused by packing them in charcoal and the charcoal dust getting in the joints. However I might end up using some combination of that process. I do not have much of a problem heat bluing barrels and have done it several times on pistols and long rifles. It's the brazing that is the problem.
The problems are oxidization and warpage. The heating must be even and some form of atmosphere control must be used. In early Belgium they just used a lot of borax over the whole assembly and a reducing flame. It was a nasty cleanup but labor was cheap.
