This is a very special creation from BrickArms. Using a special "overmolded" technique, Will Chapman is able to hand-inject these special two-color BrickArms weapons. These are NOT painted, but two colors of solid ABS plastic molded into one piece.  Each one comes in a special "BrickArms Reloaded" blister pack.
Very limited. Very difficult to make. 
 
Modular BrickArms - hand-injected BA with pins, and sockets. Go nuts, boys.
Overmolded in Brown & Gunmetal, with interchangable double-barrels.