This used Good Time Outdoors Core 15 rifle fires the 5.56mm/.223 round. It has a 16" M4 barrel with an overall black finish. This semi-auto rifle has a flat top receiver, a collapsible stock, Sun Optics EL-1100 red dot sight, removable rear sight, and a flash hider. It comes with a hard case, lock, and one 30 round magazine. It has been fired less than 20 rounds.