All our 556 NATO Uppers can be configured to your specifications. Your 556 Complete Upper can be customized with a matched optic, muzzle device, rail, bolt carrier group, magazine, or charging handle. Our 556 Upper Receivers are turn-key and ready to shoot out of the box.
556 NATO (5.56x45mm) is the ammunition used by the standard-issue US Military M4, making it inexpensive and widely available. The 556 NATO round is extremely effective across a wide range of applications.