I recently bought a Shiloh Sharps 1863 rifle. Finish of its exterior action parts is a mottled brownish gray. My shooting-hunting partner has two C. Sharps rifles, an 1874 and a Hepburn. His actions' exterior action parts finish is a mottled charcoal gray (nearly mottled black). I think my rifle's finish is identified as pack-hardened. Shiloh's catalog photographs seem to show both types or color schemes of action finish.

Other than color differences, please identify differences, advantages, disadvantages pertaining to each of these finishes. Since both look very good, I'm curious.

Case hardening and pack hardening are actually similar processes.

Case hardening however (in today's environment) is much more controlled. It is controlled in the carbon content of the medium used, the temperature used, and the depth attained. Modern case hardening furncaces are quite scientific.

Pack hardening is simply use of a hi carbon material such as leather or bone, and the metal parts are packed with this medium and set in a fire (forge) to bring up the temp to allow some carbon to enter the surface of the metal. It's just another way of case hardening but not as scientific as true commercial case hardening.

My next Sports Afield column is about Color Case Hardening.

Case hardening is a process where carbon and sometimes nitrogen is added to the outer layer
of the steel . A number of methods are used ,usually with gas .An older method is 'pack hardening' as descibed above.
If you want to 'color case harden ' this is done by the pack method where organic matter is adde to give that mottled color.This is a skilled process that comes after a long learning curve !My Turnbull color case hardening is beautiful !
Understand that the color case hardening is often done for looks rather than strengthening the steel. The cheapest color hardening is now painted on !!!

SDH - great article last issue on rust bluing

Thanks butch, I think the case color explanation might be a bit more in-depth than seen here.

quote:

My next Sports Afield column is about Color Case Hardening.

Great! Have always been interested in this!

To expand a little on Mete's explanation.

Color case hardening is intended to be cosmetic, and only hardens 0.010" or less of the surface with carbon. It can be done using the pack method where the part is packed in carbon plus bone, leather, coffee grounds, or whatever works for the maker. I'll put a disclaimer here and say most of the time, since you can harden deeper and get colors, but this isn't typical.

Case hardening ends with a dunk into a water tank that typically has air bubbling through it. Why? To get oxides and nitrides to form on the steel surface, and therefore colors. The colors are not in the steel, they are nitrides and oxides of manganese, phosporous, and iron on the surface. This is why case hardened parts are more corrosion resistant that bare steel. Old arms weren't lacquered like they are today, and case hardening provided rust protection, and beauty. These days you can get colors using gas furnaces as well, and injecting steam into the furnace at different temperatures.

So, pack and case hardening are almost the same process, but case hardening has extra steps involved to get the colors.

I hope that I haven't muddied the waters.