I wouldn't believe Uberti's are pack hardened with the actual bone and wood charcoal like ,say,Turnbulls. The metal is probably hardened in some fashion though and the color case is chemical applied which used some heast but not like the red hot for hours pack hardening. The gun metal is probably actually pretty low in carbon so it can be hardened some but wouldn't get brittle and need tempering to bring it back from the "too brittle".
Even real case hardening colors fad. Some guns hold the colors better than others depending on the depth of the case colors. The colors are actually made from the heat and the quench as the water hits the steel and cools it and leaves the "heat colors". You know...different heat temps make steel turn different colors. The parts fall into the water and cool at different rates on different parts of the piece and the different temps on the areas leve different colors. It's all "heat colors". What makes the difference between real case hardening and chemical is that the real stuff actually has "globules of carbon" on the surface as seen under the microscope. Like a mountain range in "micro size". The globules of carbom adherring to the surface reflect light differently. The gases in the crucible where the parts are packed in the wood/bone charcoal contain crbon and the carbon reacts to the steel molecules and attaches.
Anyway....I'd have to get my research papers out with an article I have that explains a lot of what the real case hardening actually is. The article states that no one knows for sure what the actual activity is exactly where the cae hardenind reactions take place. It's still a mystery for s lot of what actually happens.
What is known is that carbon enters the steel on the surface only so deep into the steel. The longer the steel is held at what they call the "critical temp" the deep the carbon gets into the surface.
In the old days.....they learned to harden metal with getting carbon into it by taking the gun parts that were relatively mild steel and some iron. The encased the part in a clay with organic articles inside with the steel. They found wood and bone charcoal seemed to work best. The gun metal was wrapped in leather sometimes too.
The parts in the clay were put in a fire and left to get red hot for a period. The clay with the parts in it was then thrown into cold water. One time,it is said, that the clay holding the gun parts cracked just as it was being thrown in the water. The gunsmith noticed thst the parts turned different colors in different areas and the colors were pretty. Gunsmiths learned people lked the colors too. The colors began to be a visual sign the parts were hardened. People wanted the colors since that was proof the parts were hardened and hardened parts people learned lasted longer.
Gunsmiths then realized that if they cracked the clay just before the clay with the parts was thrown into the water the colors appeared on the parts and proved the parts were hardened.
Anyway....the parts in the clay were quenched with the water getting into the crackes in the clsy and cooling the steel at different rates in different asreas and leaving the different "heat" colors on the steel. That's all the colors are. Heat colors with the carbon globules on the surface retaining the colors. There's a whole spectrum of colors left on steel from cooling at the different temps and the colors just became a visual sign the metal was hardened and that became the proof people wanted that their gunparts were quality and hardened properly. The colors on the steel were discovered by accident when a gunsmith threw his clay enshrouded parts in the water when the clay was cracked cooling the parts ast different temps in different areas.
Anyway..gunsmiths learned the colors didn't last real well so they began to cover the colors on the steel with laquer to protet them. The laquer wears away eventually and then the colors begin to fad eventually too.
Under the laquer or before the gunparts are laquered,if they even are, the real case hardening isn't gloss. It has a certain matt to it. That certain unshiny look to it. That's one way to tell the real stuff. It ain't real shiny. Photos may make it look like it is more shiny than it actually is. I've read that a real case hardening has a file slide over it without scratching. Like the case of carbon is as hard as a file.
The steel used in gunmaking wasn't real high in carbon and is relatively mild and resilient. The encasing of the parts in carbon rich steel makes for better wear resistance and actuall does make the piece harder on the surface to asvoid deformation. You know...like a percussion revolvers hammer nose needs to be resilient but still able to withstand the beating. The carbon surface helps the part keep from deforming longer and the relatively mild steel core retained the parts resiliency. Case hardening means the part is encased in a surface of hard carbon rich steel. The steel used back in the day was mild since steel manufacturing was still evolving.
I just read something on that and the gun steel that was evolved more was shipped in from Sheffield England and from the Bessemer blast furnaces invented by Mr. Bessemer in England also. No one in the US was able to duplicate the quality of the Sheffield or Bessemer steel for decades. The Sheffield steel was simply discovered to haphazzardly be produced where the ore was different and had qualities to it not found anywhere else in England or the US.
Later they found that they could heat flat sheared off steel pieces for awhile in a certain envirinments and get the pieces to soak up carbon thru the whole flat piece. Then they discovered they could do the process again and get more carbon in. Shear steel was discoverd then resheared steel. bacically it went somehow like that. Finding good gun steel was a problem back in the day. At one time the best came from England from around Sheffield England and from the Bessemer furnances in England. The Bessemer steel wasn't able to be produced in the US and attempts to duplicate the Bessemer process wasn't successful in the US for a good long time. Bessemer did a ting where a huge air supply was blasted thru the furnace and that somehow got carbon into the steel. It's amazing what the people went thru to make good steel and amazing what the gunmakers went thru to find and get the good steel.
Anyway....in the beginning the more mild steel they had to use needed some help and the case hardening was what they had to use since they didn't know what else to do to harden the steel well enough. Steel is just iron with carbon in it.
When Winchester finally began to use smokeless powder they took the heavy octagon barrels for black powder cartridges from the 1886 lever action and replaced it with a thinner round barrel since the better steel was discovered that would withstand the pressures of smokeless without being so heavy walled . That's an example.
Anyway......I wouldn't say the Uberti's are case hardened for real. They have the color case not the case hardneing.
Cyanide was used to color steel as an easy way to do it. The cyanide was just a medium to heat parts in where the parts would be a uniform temp throughout and be protected from ther atmosphere getting to the metal and oxodizing the surface instantly and ruining the ability of the metal to get colored by the quench. If air gets to the parts in pack hardening just before the quench the colors don't appear and it's the same with cyanide but the cyanide covers the metal so air can't get to it. The parts in cyanide coloring are dipped into the quench slowly and the heat colors appear on the steel simply from the heat at different temps coloring the steel. Heat colors. Not real carbon cased.Like cheating on the process. Get the colors and the hell with hardening the steel. Gunsmiths didn't have to actually harden the steel since it was already hard. The red hot heat of the cyanide bath softened the steel and then the water quench rehardened it. The process is just for the heat colors to the metal and not a carbon surface. Just the colors from the different temps the parts quench at when they are placed relatively slowly into the quench water.The cyanide parts aren't really dumped in. You can get real nice tiger striped colors to the parts from lowering the parts and stopping an instant then lower then stop then lower then stop. Kinda fast but not just dumped. The NEF shotguns have that cyanide bath quench look to them. Like stripes of color.
Cyanide may add carbon to the surface but I see it as a simple faster way to get colors. Some gunsmiths may have used scenarios where they splashed water on the parts to get that random colors to the metal like the real case hardening.
Anyway with the cyanide coloring the metal was usually laquered to protect it.
Sometimes even the real pack hardening is laquered. That makes it look more shiny then it really is.
Anyway that's about the way it is in a vague unprofessionsal simple guy talk way the best I can relate it.
Other people probably know more about this than I and probably could type it out better too.
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