The Nickel Boron Coating is what you're paying for on the Fail Zero BCG. It has several advantages. Nickel Boron is extremely hard, over 60 on the Rockwell C-Scale. This does not allow for it to become impregnated with any foreign matter, or become "charged". This is important in a dirty operating environment, like an AR-15 receiver.
Second, the coating itself has a very high natural lubricity to it. This is why they advertise it can be run dry and without any lubricant. While I would not do that, it can be done without having any galling take place. Third is because of it's extreme hardness, it will wear both itself and the receiver much less. This is especially true in very high temperature applications.
The reason for this is the greater difference in hardness you have metallurgically between two sliding surfaces, the less wear takes place over time, and overall. This is the main reason that bearings in automobile engines are usually made of a soft material like Babbitt or bronze. They wear less against the much harder surfaces of the crankshaft or camshaft. If both the bearing and it's opposing surface were of the same hardness, it would be far easier for either or both of the surfaces to gall.
The exception to this is needle or roller bearings, like the wheel bearings on your car. Because they roll and don't slide against one another, they can be of equal hardness without causing harm. The other advantage of Nickel Boron is that it doesn't allow material to stick to it easily. It has a lot of the same properties of Teflon in that regard. As a result it stays much cleaner, and is a lot easier to clean up. This coating is quite expensive to apply. Much more so that TIN, (Titanium Nitride). That is why they are more expensive than the run of the mill bolt carrier groups you see out there. Don't worry, you bought a very good bolt carrier group. Fail Zero and Young's make 2 of the finest bolt carrier groups out there.
