Done, and done. The torch and bottles are in the car, for exactly the price point you suggested HVAC guys unload their little Victor torches for. Even told the guy (he asked) it was for sights on a safari gun barrel, and even in CA his reaction was "I'm glad they're going to a good home!"
So you use pretty soft solders (max 15% Ag) rather than the 50% Ag solders. are you hearing rumblings from the safari rifle makers to use softer solders for crack resistance under recoil? Or do you simply plan on using the softer solders and less heat because the barrel is gonna be pretty thin (big hole down the middle and all).
I bought the silvalloy and flux, but I'm not married to using it per-se. but my barrel is gonna be substantial at about .25" thick walls, so it should be able to tolerate some pretty good heat without annealing it. (if an hour per inch to anneal is right, I can torch my barrel for 15 minutes without worrying about softening it..... Shouldn't need anywhere near that much time under the torch...)