The FN SCAR barrel assemblies are cold hammer-forged chrome-lined MIL-SPEC steel barrels with front sight assembly gas block assembly gas regulator gas piston and flash hider installed. Short lengths for reduced weight fast handling and confined space maneuvering; standard lengths for replacement of existing barrels; and long lengths for increased velocity and extended range capability. Assemblies can be easily installed by the user with a Torx T25 and 62 In Lb torque wrench and are ready to shoot without headspacing.