Howdy Gents,

Hoping some of the pro's on here can help me understand exactly how case coloring works, and what can be case colored. Now I know about the process of case coloring, but what determines whether or not a piece of metal can be case colored? Is it the metal composition? The way the metal was treated?

I'm interested in doing a build on a pre-64 M70 action. I'd like to have some case colored "accents" which leads me to the above question.

Would appreciate any advice you guys can provide.

Hello, StormsGSP. I am no expert, but the case-colering process in basically adding carbon to steel. If a steel is already high carbon..adding more & rapid quenching can cause cracking and or warping. I have heard Turnbull will no longer CC Ruger No. 1's without a signed consent by owner.
Having said all that, I have a pre WW1 German Mauser sporter with CC reciever..so perhaps there is a heat-treating process different from ordinary lower carbon steels?
Just remembered someone telling me Turnbull work was noted for color..not case depth?

Color case hardening, and standard case hardening are two different processes. They are very similar, but the intent is different, so the process is slightly different for each.

Color case hardening is done to put a very shallow decorative finish on the part, so the case depth is less than 0.010". Usually the depth is something like 0.005". The main concern is to get good color, not to harden the part for long service. The temperatures used are lower (1400-1450F), and the times are much shorter (depends on part size).

Full case hardening is intended to give a soft yet tough steel a hard wear resistant shell. The temperatures are higher (1550F-1600F)and times are longer to get more depth. Typical case depths are 0.015" to 0.040" depending on the part and application. The Mausers that I have looked at were in the 0.015-0.020" case depth area from the factory.

Color case hardening can be done to any steel, but alloy steels like 4140 or 4340 are more difficult due to them already being heat treated. Steels used for old lever actions, Mausers, Enfields, etc were medium carbon and had little alloy added. They were designed to be case hardened from the start so adding color to them isn't non-standard processing for them.

There is a description of the differences in the processes.

A call to Turnbull, or another reputable company offering this service would be the best way to find out what they can do.

Jeremy

Jeremy,

This is not meant to be argumentative, rather speculative. I believe your definition of Color Case Hardening is a "modern" definition though not all together untrue.

If one looks at older case hardened rifles and particularly tools, color case hardening was still used with the primary intent of hardening a low carbon steel and the coloring was a beautiful side effect.

Examining older Starret tools for example, many are color case hardened. Later they were simply case hardened as a cost cutting measure.

I could be absolutely wrong, the above is my understanding that Color case hardening went from a functional treatment with a decorative side effect to merely a decorative treatment.

Yes , you're right .So much so that some of the 'color case hardened' is just painted on !!
My rolling block repro is CCH by Turnbull -a fantastic job !
The proper work involved a lot of art rather than science .Unless they have come up with something new ,it involves addition of organic material such as scraps of leather.

I think what needs to be clearly understood is that traditionally color case treatment was a way to add a hard outer surface to the generally soft steels back in the day. They didn't have the sophisticated heat treatments we take for granted today, nor control over carbon and alloy contents. Hence making a metal that was both hard and tough wasn't possible back then, the best compromise was a case hardening of parts.

Modern rifles are made from alloy steels that can be hardened through and through, without fear of being brittle.

It's important to understand the differences in base steels, because if you take a modern alloy steel and apply a conventional case hardening treatment, you'll end up with a part that is hardened through and through, and hence is too hard. In which case the entire part needs to be tempered to reduce the hardness, which will also reduce the hardness at the surface.

Hence case coloring on modern firearms is really just an aesthetic treatment, it has no benefits in where and hardness of the part. Any steel alloy can be treated thusly, but it's just an expensive pretty and somewhat delicate finish.

Traditional color case treatments were done to provide a case hardened part, the colors were a byproduct of the process.

Nathaniel,

Yes, I would agree with your assessment. I was speaking as to how it each is done today.

Back in the day, they quenched in water and pack hardened everything so the ingredients for color were there even if the intent wasn't. It wasn't until the advent of gas carburizing furnaces that color was not part of the package.

One would need to consider the needs of the finished part if one was to have work done these days. Do you need color only, or do you also need a durable case?

You make a very good point.

Jeremy