Gun Control: 3D-Printed AR-15 Lower Receivers August 22, 2018. IN10957

“The possibility that criminals could use three dimensional-printing (3D-printing) technology to produce “untraceable” firearms, including AR-15s, is an issue of growing concern for some lawmakers. It overlaps in part with the issue of 3D-printed “undetectable” firearms discussed in a previous Insight (CRS Insight IN10953, Gun Control: 3D-Printed Firearms). Defense Distributed, a federally licensed firearms manufacturer, recently uploaded 3D-printable computer assisted design (CAD) files on its website for an AR-15 type rifle, including its lower receiver. The lower receiver is the “controlled part” of an AR-15 under federal law and, thus, the main component around which a fully functional firearm can be assembled. Defense Distributed demonstrated that a 3D printer could be used to produce an AR-15 lower receiver out of a polymer material, but functional reliability appeared to remain an issue. On July 31, 2018, a federal judge granted a temporary injunction preventing Defense Distributed from leaving those files posted on its website. These circumstances have called attention to the fact that it is legally permissible for any person to build a firearm, as long as that individual is not prohibited from possessing a firearm and does not build it with intent to sell it. Unlicensed firearms builders are not required to identify their firearms with a serial number and other markings. If later lost or stolen, and used in a crime, it would be difficult for the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) to trace such firearms back to their builders and possibly determine sources and patterns of firearms trafficking. Consequently, those untraceable home-built (“do-it-yourself”) firearms have become known as “ghost guns.”

…Since 1963, the AR-15 has grown in popularity with the gun-owning public. It is used in marksmanship competitions, including the National Matches authorized by Congress in 1903. The AR-15 can be built in, or modified to accept, a wide variety of cartridges, including cartridges commonly used for hunting. Many firearms enthusiasts view the AR-15 as the “modern sporting rifle,” while others also view it as a good option for self-defense. However, gun control advocates view the AR-15 as an “assault weapon” that criminals have used in some of the deadliest mass shootings. They note further that AR-15 “ghost guns” were used in two mass shootings in California. Under the Gun Control Act of 1968 (GCA), the definition of a “firearm” includes the frame or receiver of any such weapon. A “receiver” is the basic component of a rifle to which the barrel and stock are attached. It generally houses the breechblock, bolt, hammer, and trigger. In pistols, revolvers, and break-open firearms, it is called a “frame.” The “receiver” or “frame” is generally the “controlled part” of a firearm. Some firearms like the AR-15, however, were designed with a lower and upper receiver. ATF ruled that the lower receiver is the “controlled part” of an AR-15…”