The only reason I can think not to shoot it is because the fire can have significant effect on the metallurgy, leaving you with a "mystery metal". You don't know how it responds to impact or stress, amongst other things.
Your springs are pretty good proof of this, but they may not tell you much about the rest of the gun. If they're weak, they've either yielded or softened. You could check one of them with a file if you're dead set on shooting it. If they're soft enough to file easily, there's a good chance that the rest of the gun has annealed slightly, as well. Still no guarantee, though.
I wouldn't shoot it until you know more. Even if I ever decided to shoot something like that, I would do extensive penetrant or magnetic testing on all of the components that would see impact or pressure, and a few other critical locations, then I would do some kind of "proof" testing from a position far away from the gun, and then I would do the penetrant and/or magnetic testing again. Also, I'd try to hit it with a sono-pen or something to try to know its relative hardness.
Yeah, I'm over-analyzing it. Sure, it would probably be fine to shoot. But, I'd still rather be safe, and not have any worries. My last used Blackhawk cost me $400. I consider that cheap in comparison to shoot something of unknown strength.
I still would like to see pictures.