I’ve always been curious about the hot blue issue on these older side by sides. Is a slow deterioration, till years later they fall apart, is it certain doom or do some guns survive the process?
The hot salts attack the solder. The better the solder joint was to begin with, the slower the damage will occur. And if the solder joints were done perfectly, and you could somehow be certain that all traces of the hot salts were neutralized and rinsed away, then the ribs most likely will not separate. In all likelihood, the alloy of the solder used would also be a factor. Some doubles originally had their ribs and barrels soldered with corrosive flux. Fact is, corrosive fluxes usually do a better job of chemically cleaning and preparing the surface prior to soldering, but the residue can be problematic. The tinning and soldering process should have completely displaced the corrosive flux from the steel during soldering. Then if all of the flux residue is neutralized and flushed away, there will also be no further damage. The problems start when the solder joint is imperfect, which is common in a large joint like we have in shotgun barrels, and some of the corrosive agent remains behind in those imperfect joints to slowly eat away at the solder.
I've read that simply dunking the barrels in the hot salts begins to melt the jojnts. But hot bluing temps are usually around 275 degrees F, which is well below the melting point of soft solder.
I have seen doubles that were hot blued that had obviously survived for some time without falling apart. But if the deterioration is happening between and under the ribs, by the time you know there is a problem, it will most likely be too late to avoid a costly strip, relay, and reblue. Ribs usually seem fine until they pop, and even barrels with imperfect solder joints may ring like a bell.
