ah cant resist...for you limey dudes, that means i lack self discipline...
Heating any shotgun receiver without controlling the temperature and heat duration is potentially dangerous and can damage guns and potentially harm shooters. If a shotgun receiver is heated to critical temperature, such as that required for the bone charcoal surface hardening process to be effective, then the structure of the surface metal has been changed and the metal should be tempered back to provide some elasticity. Otherwise, the receiver may be as brittle as glass and may crack upon firing of the gun.
....Be careful if you are contemplating sending your prized shotgun's receiver to a high heat bone charcoal mechanic.. He is going heat it up to around 1600 degrees F....
....Case hardening is a high heat process which alters the surface molecular structure of the receiver metal. Re hardening a receiver can warp it. Subsequent efforts to straighten the metal, either by bending or filing can only harm the fine original metal-to-metal fit and adversely alter the workings of carefully aligned internal shotgun parts. In addition, if the receiver surface metal is not correctly re tempered after the hardening process, then the receiver metal may be too brittle and as a result, may crack upon firing....
Hey Ed, if the receiver was case hardened, it has a different metallurgy (the case) than the original steel/iron. I don't believe the process can take on a life of its own and magically make the entire piece high carbon to be brittle as glass.
Are you sure a part would be heated to 1600*.
I strongly suspect that the highest temper a case hardened piece would tolerate is somewhere around 400*. Otherwise, I believe the colors quickly start to fade above that temperature. As quenched high carbon steel will still be very hard at that point, thus only the case is hardened. I believe the professionals leave the inside alone, and can be really good at managing appearance and fit issues.
I don't think the molecular structure gets changed at all, but the crystalline structure of the steel has to change for it to harden. Lots o round and round, and I know I shouldn't add in either.
