Hi,. I'm not am expert but I'm pretty sure that silver solder would still require enough heat to compromise the lead solder on ribs etc. If the barrels are wired tight and heatsinks were used I'm sure that a gunsmith with knowledge and experience would be able to repair the gun.
It's just a thought about the temperatures involved , I'm sure someone in the know will read your post and be able to give you more help.

Rust never sleeps !