The 5.56 PDW Tactical Evo 7.5" Upper is a short barreled pistol piston upper that incorporates the patented Adams Arms technology and the Samson Evolution extended free floating forearm. It comes with our proprietary Melonited heavy contour barrel and pistol length gas piston system. Because the piston chamber is the same size as the chamber on the rest of the Adams Arms gas lengths this 7.5" upper now has the proper dwell time to get cyclic rate and bullet velocity needed to make this a viable short barreled option for any CQB scenarios. We've also added a 7" Samson free floating Evolution forearm giving the shooter the ultimate tactical option in a personal defense weapon. This creates the shortest, most reliable, and accurate complete upper.