556 NATO (5.56x45) is the cartridge used by the US Military M4 carbine and many other NATO weapons.  223 WYLDE and 556 NATO rounds are effective in the rifle configuration across a wide range of barrel lengths from the 14.5" standard on an M4 carbine up to 24".

Any 556 NATO Upper Receiver we sell can be configured to your specifications before adding it to the cart.  We offer matched muzzle devices, rails, bolt carrier groups, magazines, and charging handles to make your 556 NATO Upper Assembly turn key and ready to shoot out of the box.

AR15Parts.com components are sourced from top US manufacturers including Aero Precision, Anderson Manufacturing, Ballistic Advantage, Shaw Barrels, Swan Machine, Wilson Arms, Wilson Combat, ZRO Delta, and others. Each upper assembly has options to select Rail, Muzzle Device, Bolt Carrier Group (BCG), Charging Handle, and Magazine. Additional parts are available on our website.

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