This was my thoughts as well. I could get it all set pop the barrel off and do the rust blue.He uses the gutter to boil the long parts which converts the hematite to magnetite for conservation purposes. For bluing he uses a steam chamber in the process of rust bluing. With rust bluing you could solder the parts on the barrel when in the white then blue the assembly as the heat isn't sufficient to melt the solder. Hot salt bluing will melt the solder.