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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 is as brittle as glass and may crack upon firing of the gun.
Incorrect tempering of receiver surface metal is the inherent flaw in the use of the high heat bone charcoal process when applied to shotgun receivers. A dangerous situation may develop as a result of incorrect tempering of the receiver surface metal after the high heat bone charcoal coloring process is completed. This is particularly true of older shotgun receivers, made prior to ww2. Factory tempering specifications were inconsistent, as receiver metallurgy formulas changed from time to time. Unfortunately, much of the original factory hardening and tempering specifications have been lost. Even the best of mechanics are only guessing when they attempt to correctly re temper a shotgun receiver after subjecting it to a high heat bone charcoal hardening process.
Quality case coloring should provide cosmetic enhancement without endangering gun integrity or shooter safety....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 1500 degrees F... Make sure that you get it in writing, that if the receiver warps in the heating and tempering process or that if it cracks after firing, then the mechanic will assume full financial responsibility for the destruction of your gun and/or your personal injury.
A low, controlled heat process, combined with specific chemicals is the safest way to recolor a shotgun receiver. So long as the heat is kept low and controlled, the original receiver metallurgy and heat treatment is not changed. No harm is done to the gun nor is there any potential for danger to the shooter, as a result of the re coloring process.
In summary, shotgun receivers should never be rehardened in the vain interest of restoring the cosmetic effect of case colors. Case hardening is a high heat process which alters the surface molecular structure of the receiver metal. Rehardening 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 retempered after the hardening process, then the receiver metal may be too brittle and as a result, may crack upon firing.
Last edited by ed good; 05/25/13 08:25 AM.
