Others here have already mentioned why gunsmiths won't work on them, so I won't get into that. Since you don't really have anything to lose with this gun, trying to do it yourself is probably your only option unless you want to sell it for parts and buy something different. Is it the frame that broke, or a part in the cylinder and crane assembly? I've never heard of a "pivot tube sweat joint" but if you look on Numrich's website, there's a parts diagram. Find what the part is called and search for it. If you can't find it, call Jack First Gun and they'll probably be able to make one for you. If the gun is worth that much to you anyway.