This upper offers a 11.5" 4150 QPQ barrel with a 1:7 RH military twist rate. The Flash hider is 5.5" long and pinned for NFA compliance. It is also made of chrome-moly steel and HP tested. Our barrels are Mil-Spec. The upper is C7 A1 Mil-spec and at a length of 16" it's pretty darn short. The flash hider is pinned on to be NFA compliant. We recommend a 55gr or 62gr bullet for best accuracy. The front sight is a A2 with bayonet lug using taper pins to install.