FN America Barrel Ar-15 Button Rifled 14.7'' 17 Mid-length Gas Govt. Made with the same care and feeding regimens as the FN rifles these barrels are born with a precision rifling and gas port system like carbine barrels. Furthermore button rifle barrels lend themselves to greater accuracy over longer barrels with less weight. In fact FN barrels with longer gas port systems have a higher margin of error for consistent tighter groups. No load-bearing feature like a gas block needs clearance The barrel ships with a carbine gas system and a 1:7 twist rate. However carbine barrels do not fit as a mid-length gas gun barrel and require a rifle-length gas system. Specifications for FN America Barrel Ar-15 Button Rifled 14.7" 1:7 Mid-length Gas Govt: Manufacturer: FN America Color: Black Caliber: .223 Remington Additional Features: Threaded Package Contents: FN America Barrel Ar-15 Button Rifled 14.7" 1:7 Mid-length Gas Govt