I decided on a color ratio of 0.579 to 1.0, flat (SOCOM) black to flat gray-black. (19 mL gray-black to 11 mL black if my math is right there...) My initial estimate of 30 mL was off, and I ended up mixing up another 15 mL *two times* (super PITA) during the spraying phase, but I also wasted a lot of paint. I would estimate about 45 mL of paint should do an upper and lower receiver, a charging handle, and the trigger guard with a little left over if need be.
I wanted to ensure a flat appearance, so I heated the parts to 200 degrees F prior to coating, bringing them out each one at a time. I noticed that if you burn through the anodizing when blasting, and the surface is not uniform in the ratio of anodizing to bare aluminum, you will have "light spots" as you coat. To avoid spraying on too much at once and getting a shiny coat in the end, I would spray two or three passes at 14 psi, then return to the 200 degree oven and switch parts. John warns of this in the instructions that if the part is too hot, you will build up a rough texture like sand paper in the finished product. He is exactly correct :) However, I found that after the part had cooled, you can take a terry cloth and "rub" the part vigorously and it smoothed right out, and retained a flat finish. So going forward, it's something I'm OK knowing that I can correct it and still end up with a flat finish.
When satisfied with my coats, I hung the parts up and pre-heated the oven to 300 degrees F per John's directions. I baked mine at one hour and 10 minutes. The 10 minutes was purely for the hell of it...no other reason. Now on with the pics!
(oh, pardon the dust and paw prints on the close ups in the shop. That is not the finish, that's me handling them with filthy hands)
Color comparison to my 1:1 ratio (magazine)
The magazine on top is one that was coated in 100% "gray-black" for comparison
Results from my initial horrible screw up...I tried the 325 degrees F at one hour, 45 minutes, and it was waaaay too green and shiny for me. Be careful if you go with the green tint. I had a part I just did at 300 degrees at one hour and it still had a little green tint, so I think the paint is very touchy to exact temperatures (as others have stated). This charging handle latch shows the results of that batch compared to the final finish. I left it because it's a steel part, but there's a big difference. Do note, though, that if you botch a project, you can always take it back to the blasting cabinet and start over. There *is* a reset button ;)
Others have suggested letting the parts sit for 24 hours prior to assembly. I felt confident that they were fully cured, and proceeded with assembly and didn't experience any problems. Again, forgive the greasy paw prints from reassembly all over the receivers.
The next day, I took it outside to grab some photos in direct, and indirect sunlight. Indoors the color is a little deceiving and looks dark. It almost made me wish I had made a lighter batch of paint. However, outside in "real" lighting, the gray really pops. I'm very happy with it.
Overall I'm very pleased with Norrell's Moly Resin, and the results. It's very easy to work with, cleans up well, and looks great. So far it seems like a durable finish, and is actually "difficult" to scratch unlike anodizing. I think over time it will wear, but the natural wear will look nice, exposing raw aluminum underneath.
Hope these photos help if you're looking to use the product. I would certainly recommend it, particularly to us in the A2 and "retro" community. Again, I feel that pure "gray-black" is too light for A2's, and I came to that conclusion after scouring the Internet for images of folks who had used it, as well as photos of real, issue M16A2's. But given the variance out there, and the existence of light gray FN A2 uppers, I think the end-user has a lot of leverage with what is correct, and what will look good. And of course, it's your rig, so do what you want ;)
Enjoy the pics.