doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com question on case color

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 hardening process to be effective, then the structure of the 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 or shatter upon firing of the gun.

Incorrect tempering of receiver metel 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 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 metallury 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.

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.

I normally wouldn't post on a subject like this, but I've had it with the misinformation and disinformation on this board, much of it peddled by proponent(s) of "torch coloring" shotgun frames. To start with, the vast majority of prewar guns' frames are made of 1018 or 1020 steel. This is a mild steel with a low carbon content that is NOT hardenable, meaning it can be heated to any temperature no matter how high and quenched and it will not harden. It lacks the carbon content to do so. This is the reason for case hardening. There is no tempering necessary after case hardening in mild steel as the core of the material remains unchanged. Only the surface is hardened to a depth of between .002 and .005". All this talk of drawing and tempering only applies to "through-hardening" steels. No prewar American made shotgun ever used a through-hardening steel in the manufacture of it's frame. I know this because I have the factory drawings for most maker's guns. The material is called out for each part on the drawing. The only thing that torch coloring accomplishes is localized annealing of the remaining case hardened skin on the frame. I contend that this practice is more dangerous than proper case hardening. Before one makes proclamations about metallurgy and what the factories did, they should do some research. Otherwise keep your hazardous opinions to yourself.

Very well said Dewey.......I was biting my tongue myself.
Steve

Thanks Dewey, the facts period.........AMEN....!!..........

Yes, a Charles Boswell. But, most anything can be blown up if improper pressures are applied.

the use of the term torch case hardening infers that the heat source is uncontrolled. i agree, uncontrolled heat applied to a shotgun receiver is a bad idea. almost as bad as heating the receiver up to around 1600 degrees, beyond it's critical temperature and then guessing at what is the correct tempering procedure.
as for research, it ignores reality. the reality is that i and others with far more experience than myself, have seen too many fine pre war guns ruined by high heat case coloring mechanics, who guessed wrong, when they attempted to temper the receiver metal after the high heat bone charcoal re hardening process was completed. the wisdom of experience says not to alter the original factory heat treating in a vane attempt to restore case colors.

Boy,...how I wish Oscar was still with us

Maybe we could light a 'torch' for him...

There is NO tempering involved in case hardening! The material being case hardened is not a through-hardening steel! There is also NO guesswork involved. I am done trying to piss up this rope. Keep doing what you do and I will keep correcting it.

Obsolete material + obscure process + misguided charlatan = eczema. I'll settle for the "ephemera" of case hardening in "protected areas" or graying down. Heat eyes belong in scrap boxes or on steel sculpture.

jack