Check out the following link.
www.kgcoatings.comThis is a very durable finish that is stated to have been developed for military use.
A local smith/friend of mine has done several for myself and family members using this product. It is far and away the best I have ever come across. It can be done in a few different colors/shades as well (Most of mine are granite grey instead of matte black).
I have a custom bolt gun that was teflon coated when built that already shows some wear. I have another bolt gun that was finished with the KG product and it is several years old and still like new.
Also, it must not be to expensive because my smith only charges $75-$100 to do the job, versus $200 plus for teflon.
Hope this helps.
Smoky