Chemical blackening of stainless steel barrels that are fitted to CM action is very possible, I own several rifles that are all matte black and match perfectly, despite having 2 dissimmilar metals.
The finish is very durable, just as durable as blued steel.
I only know of 1 shop in Canada that does this process, there may be others I do not know of though.
HWSNBN has done several rifles for me in blackened stainless. Excellent work and lasts up well. I have had several other rifles coated with different coating, none have stood up as well a chemical blackening. Coatings are just that , a coating , and how well it lasts is all dependent on how much residual oils remain in the steel. Needless to say prep work before a coating is applied determines how well it will stick.
Chemical blackening actually changes the color of the steel, it like blueing is a form of controlled oxidization.
I saw LRCs Dakota posted several times on this forum maybe he would like to show it off again it was chemically blackened by HWSNBN.
KK