silver soldered once but it did not hold.
Are you sure that you used "silver solder"? Or, was it "soft solder". True silver solder requires the metal parts to reach red heat. If the solder you used did not require red heat, the part was only soft soldered and certainly would not hold. If you do not know the difference between silver solder and soft solder, you should take it to someone who does (a gunsmith).