Chambered in 5.56x45mm NATO (223 Rem.), the FN FS2000 Series are semi-auto only variants of the proven F2000 selective-fire bullpup carbines. The FS2000 Standard comes equipped with a 1.6x optical sighting package, while the FS2000 Tactical offers an integrated MIL-STD 1913 top mounting rail and emergency backup folding sights. The FS2000 carbines are gasoperated and use a rotating bolt lockup for reliability and greater accuracy. Both variants have 17.44" cold hammer-forged MIL -SPE C barrels and muzzle brakes. Fired cases are ejected through a forward port away from the operator. Models with 10- or 30-round detachable box magazines (DBM) are available. The polymer stock is fully-ambidextrous. An accessory FS2000 Tactical Fore-end is also available that provides three MIL -STD 1913 forward mounting rails.