your lighting is blobby, your shadows are weak, and using the same grunge brush 1000 times to add "damage" looks really bad. it looks like a bunch of white x's on the stock. the stock material is not supposed to be metal (if i recall what you said correctly) and the base that you painted looks hardly like metal or synthetics.

post a render of the skin on the model. i want to see that. don't forget to credit the author, either.