doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Need help on case color, among other things.

I came across an English gun made in 1903 (per maker�s records and proof marks consistent with that date) the case color is like new. The barrel�s bore appeared to have been honed and there is a very slight play in the barrels against the fences. Other wise the gun's appearance is more like a well cared for 20 year old gun rather then one over a hundred nine years old. Further, it does not look like a recent rebuild.

My lone experience re case coloring a gun is that the case color doesn�t take well if the surface of the gun has been previously case hardened. I had thought to get secondary colors you have to either, first anneal the case, grind off the surface hardness or heat treat with cyanide.

I would most appreciate your help unraveling my little mystery as it would do much to advance my knowledge of old doubles. Thanks

Annealing is the usual precursor to a charcoal re-case job. It allows the stresses from the previous process to slowly dissipate without affecting the mechanical integrity and to some extent reduces the carbon content of the hard layer. In fact, the whole shebang reverts to mild steel, so if you want to do some engraving or fitting, this is the point to do it.

When the re-case is done, the heating of the charcoal packed round the parts produces carbon monoxide which reacts with the iron giving a new carbon rich surface. When quenched this is what gives rise the hardened layer and the colours, and also the surface stresses. Properly done it gives very pleasing results; just as good (if not always the same) as the original.

Molten cyanide was once widely used as a carburising agent (ie supplied carbon to the iron surface just like charcoal does) prior to quenching, but it would have no part to play in annealing. In any case (oohh!) it's virtually a bygone process now for obvious reasons. I've never heard of grinding the case off a gun, but who knows? There are some strange things happen in this world.

If the case on the 103 year old gun in question gun looks like new, it probably is.

Eug

The next questions being:

How long many years will the case colors retain their intensity if proper care is taken.

The cost one can expect to have a receiver and ejector iron recased.

Thanks

As for the longevity question, I have a Westley Richards bar in wood eight gauge that was made in 1872. The colors on that gun are still 100% coverage and vivid if not shiny. I doubt that they were shiny when new. I have long felt that the opinion voiced by some that colors are destroyed by time and exposure to light are nothing but "old wive's tales". How would they know?

A remark or so on the annealing. The ability to engrave the part is not really dependant on the % of carbon present, but its hardness. I do not have any positive figures on how much, if any, of the carbon would actually migrate out of the case in the annealing. Primrily though I think it simply does just as it name implies, IE it anneals it or removes the hardness. I do not see that it would revert it to mild steel, which is a term ordinarily given to a low carbon steel not subject to hardening by heat treatment. The carburizing process gives a high carbon "Case" which then is subject to hardening by heating & quenching. With both in the annealed state a high carbon will be a bit harder than a low carbon (Mild) one, but not to the extent it cannot be readily milled, turned or engraved.

according to tony's fine book, the re case coloring process for shotgun receivers consists of four steps:

- annealing

- coloring

- hardening

- tempering

this discussion, like so many others on the subject seems to ignore the last step, ie: tempering.

it is my understand, that the tempering step is the least understood and most critical part of this whole process. if not tempered correctly, the receiver metal may be too brittle and is subject to cracking under the stress of firing. if tempering is over done, then the receiver metal winds up too soft and makes the receiver subject to excessive wear at those points where metal moves against metal, when the gun is opened and closed.

comments?

I have never seen this Tempering mentioned in regards to the Color Case Hardening of guns. I do know that the years I spent in machine shops, partsre sometimes carburiced & hardened, (case hardened) though not for color. They were always tempered at a low temp, usually around 300�-350�. Not high enough to significantly reduce the hardness of the case, but to sort of de-stress it. I once saw ths tempeing step omitted by a young trainee who was making a set of paralells. He had sucessfully hardened them, left a bit of stock & dusted them off on a surface grinder for size & paralellism (A common practise). However by the following day their surfaces were filled with little hairline checks (cracks) remdering them totally useless.

I always thought the colors were lost from just use over the years. (Post up some pics of the WR 8).

piper: sadly, i too have seen those same hairline cracks. problem is, they were on a parker dhe receiver that had been recolored by some guy with just enough knowledge to ruin a fine gun.