02-26-2014, 04:37 PM
Nitriding is also known as ferritic nitrocarburiation, Melonite, black nitride, salt bath nitride, etc. is a metallurgy treatment that changes the surface of the steel to a much smoother and harder condition, without changing dimensional thickness. Glock has been using it on their slides for a long time now, as have other manufacturers. The Swiss national assault rifle uses nitrided barrels, and they are the highest quality of craftsmanship of any assault rifle design I have seen with the SIG550 series.
I have several AR15 barrels in .223 Wylde that have had the process done, and they are extremely hard. A common steel file will slide off the surface of the barrel, for example.
The Army tested barrels coated or treated with the following methods and issued a report in 1958 about their results:
* Hard Chrome lined
* Titanium Nitride lined
* Nickel Boron lined
* Salt bath nitrided
The excessive shock forces of continuous automatic fire were best dealt with by the hard chrome lining, so this is what was used on the M60, and later M16, then SAW.
Salt bath nitride treated barrels don't really foul that much at all, since there isn't much for them to allow residue to purchase to. There is more surface lubricity, so you might get lower velocities with a given load, but the ES and SD should be tighter. You might have a bit more room to play with in pushing the velocity, as the smoother surface allows a deeper primer jump of the projectile, and less resistance to engraving pressure.
The actual cost of the process is about $5 in optimally-sized batches. Barrel life can be extended by about 30%. With the Grendel, we have a throat and barrel life that is unusually long compared to other center-fire rifle cartridges.
I have several AR15 barrels in .223 Wylde that have had the process done, and they are extremely hard. A common steel file will slide off the surface of the barrel, for example.
The Army tested barrels coated or treated with the following methods and issued a report in 1958 about their results:
* Hard Chrome lined
* Titanium Nitride lined
* Nickel Boron lined
* Salt bath nitrided
The excessive shock forces of continuous automatic fire were best dealt with by the hard chrome lining, so this is what was used on the M60, and later M16, then SAW.
Salt bath nitride treated barrels don't really foul that much at all, since there isn't much for them to allow residue to purchase to. There is more surface lubricity, so you might get lower velocities with a given load, but the ES and SD should be tighter. You might have a bit more room to play with in pushing the velocity, as the smoother surface allows a deeper primer jump of the projectile, and less resistance to engraving pressure.
The actual cost of the process is about $5 in optimally-sized batches. Barrel life can be extended by about 30%. With the Grendel, we have a throat and barrel life that is unusually long compared to other center-fire rifle cartridges.