FN SCAR 16S 10" Barrel Assembly. The FN SCAR barrel assemblies are cold hammer-forged steel barrels with front sight assembly, gas block assembly, gas regulator, gas piston, and flash hider installed. Available in short lengths for reduced weight, fast handling, and confined space maneuvering. This barrel will only fit FN SCAR 16 rifles chambered in 5.56 NATO.