The scuff marks are a little too intense. from looking at the recent screenshots. it looks as if this gun has been dropped on the ground for a month on a road and cars and trucks have driven over the top of it. I believe this is because the damage on the gun is alittle off from places it normally is. Any chance for reference photos?
I would recommend doing a paint over ontop of the gun. and mark out places where damage is going to occur.
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Then review the current grime and damage and see if its in the right places.
I would also suggest adding other elements such as grease and other evidence of damage or paint work onto the gun.
looking great pete, great seeing this evolving.