This gun came in to repair a failed rib "tack down" job and turned out to be a shining example of the consequences of such half-assery. At some point in the past, the Brown featured here had experienced a partial rib separation, which, to properly correct, would necessitate the complete removal of all ribs and forend lug. It seems that whoever was responsible for this mess didn't think that all of that work (and expense) was necessary. Their brilliant idea was to simply use lots of acidic flux to get the solder to adhere to the steel. Clearly, our hero gun-plumber either didn't know, or care, about the consequences of leaving that acidic soup between the ribs (I'm betting that both are true) because the job was "done".
Yes, the foul stew that is American (and English) gunsmithing, which seems to consist of equal parts ignorance, incompetence, arrogance, witchcraft and hubris, has provided yet another bad example for your viewing pleasure.
After removing most of the rust:
If some of those areas of pitting look pretty deep, it's because they are. Here is one of the tubes after cutting it off.
The mating edges of the rib also suffered.
At this point, if the title of the post wasn't enough of a clue, it's clear that sleeving is the only cost-effective route to salvation for the gun. Here are some photos detailing the process.
Because I do not do "TIG" sleeving, the tubes must mate perfectly to the (now "monobloc") breech, so that the seam will be invisible. If you think that TIG sleeving is a good idea, have at it, but I prefer not to have the chamber and the rest of the tube be joined by a brittle HAZ. There is probably a good reason that no factory monobloc designs are welded.
After the time consuming job of filing new mating surfaces on the top rib, the whole works are tinned, cleaned, rosin fluxed, fixtured and soldered into an assembly.
At this point, the barrel assembly would be cleaned and the chambers and extractor bed recut, but, we have a bit more fuckery to remedy. You see, when the barrels were last "repaired" and reblued, our hero polished the breech faces of the barrels to the point that the barrels are now off the face. Now, the typical jerk-off "gunsmiff" would get out their TIG torch, weld up the barrel hook with a birdshit mess of weld, then use a Dremel tool in a futile attempt to get the hook to actually fit the hinge pin, blissfully oblivious to their own idiocy. Because the hinge pin in this gun is screwed in, I made its replacement from O1 so that it could be heat treated (through hardened and tempered).
The finished (and heat treated) pin installed:
Followed by the original outer cover screw:
Now, the barrels are blacked down and the chambers and extractor beds are cut. Notice the red grease on the frame knuckle? That's there because the forend iron is in place during the blacking down process. This is because the forend iron's function is to pull the barrels tight onto the hinge pin, stabilizing the joint. That's why one does NOT remove the forend to check if a gun is off the face.
You'd think we were near the end but, no, there is more dipshittery to correct. Apparently, someone thought that they could make a toplever spring, in two parts, welded together.
Naturally, work of this caliber wouldn't be complete without at least one trashed screw slot.
The chokes are adjusted to the client's specifications and the barrels are polished in preparation for recutting the engraving and rust bluing.