I think maybe you’re thinking of Birdsong’s Black T?
Cerakote was big for a while but it’s popularity wore off as quickly as the illusion of its durability did which is to say not long. It scratches and chips.
I have just recently had a rifle finished in Black T and it looks great but hasn’t seen enough use to know whether it’s a big improvement over cerakote. I would like to try Nitride linked in the post above.
One other to keep in mind, particularly if you’d like to roughly imitate the look of brushed SS, is Mahovsky’s Metalife which is a plating rather than a coating so it molecularly bonds to the surface of the steel. I had one rifle so finished but sold it before durability came into play.
Yes that's it it was the Birdsong's Black T thank you!
