It has been years since I soldered SS, and things may have changed, but basically, the answer is, "yes". When I was soldering 304 and 316 SS, we had to use an acid flux (probably methel-ethel-death these days, and totally unavailable). For gun work, especially ribs, it would mean that somehow you would need to be able to clean up all the flux under the ribs, because even on SS, the acid would start to eat away at the steel.

That said, I am not sure what kind of SS steel Ruger is using in there Red Labels, it may be a .416SS, which is magnetic and barely qualifies as SS. I believe that .416 is more easily soldered, but, to my knowledge, I have never done it.

Brownells sells #4 Comet flux which I have used, is an acid flux, and claims to work on "all metals except aluminum". This flux is extremely corrosive and I gave up using it on guns years ago, but as a flux, it works extremely well. You just need to be able to clean all the flux up (which is harder than it sounds with this flux) - it needs to flushed, even boiled repeatedly to get it all out of the pores in the metal. The most minute leftovers will cause serious rusting. There may be some way to "kill" the acidity of flux, (boil with baking soda??????), but I don't know for sure.

Yes, SS can be soldered, but with "issues". These can probably be overcome and somebody out there probably has more experience with this than I, so I will be interested to hear what they have to say.

Ellis