By now anyone in law enforcement or who follows the news has heard of the AR lower receiver built and successfully tested using a 3-D printer. This technology uses an additive process where a polymer is built up into the shape you want. Since the lower receiver is the only part that legally constitutes the “gun,” once you have that you can order the rest of the metal parts you need and build a functional AR. Under federal law, anyone can manufacture a firearm with no license or serial number as long as it is for personal use only and not sold or given away.

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