Bued? or other coating?
My AMD 65 appears to have been blued originally. I have a bottle of Brownells Oxpho-blue and have rubbed it down a few times with this. It has blackened thing up. I'm assuming that the AMD's were not painted with anything, just blued?
Where the Oxpho darkens your gun, it's not painted. FEG used a baked-on blue-black paint finish originally, but where it's worn off you could darken it with cold blue. FEGs exported to the USA pre-ban had a low-luster black finish. Post-bans had a glossier blue-black finish. All the AMD kits are rather crudely refinished here in the US after assembly into the required legal configuration. This is probably some kind of air-dry paint judging by how crummy it is. I'm going to refinish mine someday and use a bake-on Gun Kote or Dupli-Color Ceramic Engine Enamel, Low-Gloss Black. This is heat-resistant and can be oven-cured at about 250 degrees after it dries. The original-finish FEG AMD kits I've seen again seems to be a low-luster baked-on coating. You can find pictures of the real thing in use in the Middle East. Most of these are in various stages of finish wear, and it looks like paint wearing off rather than blueing.