I bought one of the first of Mr. Brown's books on building double rifles and have read it several times. You are right, he is oppinionated on some things, and his way may not always be the best way, but as you say, It is just about the only game in town. You only mentioned one supplier that I have not heard of or used, who or what is Jeff's Outfitters? I have never heard of them before. I know of several more that might be of some help but the reason I asked the question about suppliers is to see if I had missed any serious sources. Barrels can be had from many sources, and yes, I too have salvaged parts and reused them. It is one of the best ways to get them if they will work for the purposes you need to fill.
Tom Ondrus has been selling me parts and guns for several years, and he has many nice parts including monoblocks, sleeving barrels, and all the parts to build a double from scratch. He unfortunately only has one style of rib, though, and sometimes I need something shorter or narrower so I am always looking for other sources. Track of the wolf, Dixie Gunworks,Bauska Barrels in Montana, De Hass barrels in Missouri, Hastings barrels, I have used all these and more. I will take parts where I can find them, and I just thought it would be informative and helpful to have some kind of master list for everyone to access, especially the beginners on here.
Bob H.