Advancements in milling and 3-D printing technology have made it easier than ever to build your own guns, reports the San Diego Union-Tribune. The guns often are assembled in garages and basements from mail-order parts. They are nicknamed “ghost guns” because a lack of serial numbers make them untraceable. The guns are technically legal, but authorities are concerned about the potential for a growing black market that sidesteps state and federal laws.
The build-your-own-gun movement took off a few years ago in California, home to some of the strictest gun laws in the nation, and has more recently been spreading to other parts of the country, said Paul Ware of the ATF in Los Angeles. Gun manufacturers are required to engrave identifying information on a weapon’s lower receiver that allows authorities to track its maker and chain of ownership if the gun is used in a crime. DIY gun-makers can buy unfinished–and unmarked–lower receivers online. The unfinished piece can be sold legally without a license as long as it is missing key components that make it a firearm.