Just put my new generic (I think it is a RRA) M4 flat top upper on my pre-ban lower. Two different finishes (D*#% IT!)
The upper appears to be a very flat chalky type forged appearance. Looks more grey than the lower. The lower is a normal Colt black. Sorta of a flat black, but shineier (sp? - hell, is that even a word?) more shiny than the upper.
So, what is the best way/products to refinsh your receivers so that they both match?