Visited with "Adam" at H&M Metal Processing while I was at the NRA convention this spring.
Talked extensively about their process which I understand is slightly different and improved over Melonie (but don't take my word for it, I'm not a chemist or engineer)
Originally Posted by H&M Metal Processing
BLACKNITRIDE™, or Ferritic Nitrocarburizing, is the thermochemical that simultaneously diffuses nitrogen and carbon into the surface of ferrous metals.
I was quoted $200 for a minimum fee, but that they could do multiple parts for that price. 4-5 bolts or a couple bolts and a barrel, or a few other AR parts.
I assume the set up costs the money and the tank size is the only restriction.
If you were to do a few parts...it would be VERY worth it. I'm planning to do ALL of my BCGs and all my muzzle breaks and suppressor mounts.
The lubricity of the metal after black nitride is suppose to be such that carbon won't stick to it. That's a big deal when running a suppressor.
H&M Metal Processing