In the spirit of "How, and Why dey do dat?"
I have added a very understandable link to the AWS site regarding silver alloy brazing. (Silver soldering to some)
http://www.aws.org/wj/amwelder/9-00/fundamentals.html

If one thinks about the assembly of shotgun barrels of the various styles talked about on this site, one can really begin to see how and why various techniques for their joinery have evolved.

It's not that technical of an article, and covers many of the issues a shotgun barrel set faces.
And provide some insights as to just how precisely barrel joints actually have to be filed. (not very)

Out there doing it best I can.