 At the time, the role was filled by the M16A2, which could not mount optics or night vision sights and used M855 5.56×45mm NATO ammunition, which was too inaccurate for the role.A previous designated marksman weapon effort attempted to use the M14 for the role, but it was not as accurate as bolt-action rifles and could not fit into the Fleet Marine Forces logistics system.The enhanced SSTW had to engage targets out to 600 meters, use ammunition interchangeable with the M40A1, be able to mount a sound suppressor and optics, and be supportable.