What is a 556 upper?
556 NATO (5.56×45) is the cartridge used by the US Military M4 carbine and many other NATO weapons. Any 556 NATO Upper Receiver we sell can be configured to your specifications before adding it to the cart.
Can you build an AR-15 without a background check?
Gun Fact: You Can Legally Build an AR-15 of Glock Right in Your Own Home. “Unlike firearms, “eighty percent” receivers can be purchased in a brick and mortar store and brought home without filling out paperwork or conducting a background check, or may be purchased online and shipped straight to an individual’s home.”