RUBBER CITY ARMORY - M16 Black Nitride Bolt Carrier Group

[Sputnik]

I'm still doing long-term durability, reliability, and function-testing on different BCG's dating back to 2007, in Arctic through hot-wet annual cycles. They include:

* Standard Mil-spec 8620 carrier with correct chrome-lined gas gey
* Titanium Nitride (TiN) plated BCG, including the bolt
* Nickel Boron (NiB) plated BCG, including bolt

So far, no reliability differences that have stuck out. All guns have been lubricated during high-volume shoot sessions. The TiN seem to acquire a burnish from hot gassing, and the NiB does to a lesser extent as well. Lubricity goes to the NiB favor, although no reliability differences have been noted.

The ferritic nitrocarburized (melonite) bolt carriers seem to be somewhere between TiN and NiB from just a subjective observation so far, although I didn't have any to start testing with in 2007.

More important with the Bolt Carrier is the dimensional uniformity and adherence to standards, especially with regard to inner bore ID's where the bolt inserts into the carrier. The tail of the bolt must have a good seal with the hole it penetrates through in order to have a proper gas seal for the circuit, but modern Total Quality Management standards seem to have weeded out the reject carriers that were too large in the bolt tail hole.

Any further results from this durability testing? I ask because I just today saw my first Titanium Nitride BCG (in 5.56) at a gun show here in Jacksonville NC. The conversation mentioned a Titanium Carbo Nitride process; any information on this improvement?