Enabling the operator to quickly and easily tailor the FN SCAR barrel length to suit the mission at hand, the assembly can be quickly installed in a manner of minutes with a torque wrench. The FN SCAR barrel assemblies are cold hammer-forged and chrome-lined from premium steel and include the front-sight assembly, gas block assembly, gas regulator and piston, 6 o'clock rail, and the FN 3-prong flash hider.