Re: Best coating for Surgeon action
Nitriding is a surface treatment, it chemically changes the surface layer of the metal increasing the carbon content and hardening it significantly. I use this finish all the time on personal and customer pistols (including barrels). It is an excellent finish with high wear resistance and greatly reduces the coefficient of friction between moving parts. It also makes parts much more durable due to the extra hardness. It can be applied to carbon or stainless steel with the same end result, a very dark black finish that is probably the most durable finish available.
The actual process leaves the parts a grayish color I believe, the finished black color comes from a basic hot salt bluing applied when the process is over. The hot bluing takes on the surface characteristics of the treated surface of the metal making it much more durable than hot bluing on untreated steel. It has the added benefit that when the parts eventually do show wear, you can just re-blue them to restore a brand new looking finish which will be as durable as when it was originally applied.
The only thing close to it I know of for durability is physical vapor deposition (PVD) processes like IonBond. These are coatings, but they are very hard and nearly as durable as well. These are applied at a lower temperature and may be a good choice for an action. I have used Richter Precision for this type of finishing before, they are cheaper than Ionbond and much easier to deal with. The only thing I don't like about their finish is that it is not a very dark black, it is more of a very dark matte gray (almost black but not quite).
I have not yet used nitriding on a rifle barrel. I know of people who have (not many but a well known benchrest shooter has done quite a bit if experimenting with it however I can't remember his name right now, some googling would probably turn it up) and from everything I read it will extend the service life of the barrel because the hardened bore will be more resistant to erosion. It reportedly has the side effect of reducing muzzle velocity slightly because the bullet moves more easily through the bore (due to the hardness and reduced coefficient of friction) and therefore there is less pressure pushing the bullet. From what I've read you need to increase your powder charge to maintain the same pressure and velocity. (of course this should always be checked with a chrono and some common sense)
The downside of finishing the barrel this way is that once it is done you can no longer machine the barrel. So, if/when your barrel does start to wear out you couldn't just have it set back and have the chamber re-cut, the metal is way too hard at that point for pretty much anything but diamond cutters to work on it.
I also know people treat the bolts, there are several benefits to this, namely the bolt will run smoother because it is harder. Also, any frictional wear on the bolt lugs from locking/unlocking will be virtually eliminated. *note-because of the temperature at which the treatment is applied (~1000 deg) this should only be done to one-piece or welded handle bolts, not ones that have a brazed on handle like a Rem 700. The temperature would likely damage the brazing if not make the bolt handle separate completely during the process.*
I have never seen anyone treat an action with the Nitride finish (doesn't mean it hasn't been done). I think it has been hypothesized that increasing the surface hardness that much could be dangerous in the case of an overcharge by making the action brittle and therefore prone to shattering rather than deforming. I don't think anyone wants to be the guinea pig
When I saw the pictures of the previously mentioned benchrest shooters rifle he had treated the barrel and bolt but not the action.
Not being an engineer, I am not sure whether these concerns are founded or not. To me, it doesn't make much sense since the explosive force of firing the cartridge occurs in the barrel which people don't really have a problem nitriding. I had heard the same concerns about nitriding 45cal pistol barrels because the wall thickness of the barrel tube and the chamber walls are much thinner than 9mm or .40 cal barrels but I have nitrided many .45cal pistol barrels without problems.
To me, from a gunsmithing standpoint, refinishing should always be done when all other work on the gun has already been completed.
If you decide to go with a Ceracoat type finish, I can highly recommend Brad Cummings at Cummings Custom Refinishing (
www.ccrrefinishing.com). He and his wife Mary are great to deal with and their finishes are excellent quality and always perfectly applied, good prices as well.
If I was building a new rifle and I didn't feel like being a guinea pig, I would nitride the barrel and bolt (if its not a brazed handle) to extend the service life of the gun, and have the action coated in Brad's "House Black". His "House Black" finish is almost a perfect match for a nitride finish (at least the one I use).
