Homemade guns made from unfinished "receivers" and on 3D printers are increasingly popular, and need not be registered or bear a serial number, nor must the maker-owner pass a background check.

Individuals in this country have been making their own guns for centuries. The practice is deeply rooted in our constitutional history and tradition. Legal scholars have recognized that the Second Amendment’s guarantee of the right to keep and bear arms would be meaningless in practice unless the state afforded individuals the ability to exercise that right—which includes making their own guns.

For the past almost half-century, however, the sale and subsequent control of firearms have been heavily regulated by federal law. It may come as somewhat of a surprise that even in this era of regulation, it is still completely legal to make and own a homemade gun. Even more surprising , a gun made wholly or even twenty percent at home need not be registered and the owner need not pass a background check or obtain a license.

Gun Control Legislation

The Gun Control Act of 1968 (GCA) mandated, among other things, that persons “engaged in the business” of dealing in firearms must be licensed by the federal government. (18 U.S.C. § 921(a)(21)(C).) This development made it illegal for an unlicensed person to make a firearm for sale or distribution. (18 U.S.C. § 923.) In addition, the law requires that firearms dealers must perform background checks on prospective purchasers and maintain records of all gun sales. (18 U.S.C § 922(t).)

However, nothing in the GCA prohibits individuals from making guns for their own personal use. A non-licensed person may make a firearm, provided it is not for sale and the maker is not otherwise prohibited from possessing firearms (such as a convicted felon). (18 U.S.C., Chapter 44; § 922 (d).) Federal law imposes none of the purchase restrictions on non-licensed possessors that it does on those who need licenses, and as a result, homemade guns need not be registered and the owner need not undergo a background check.

Who Is Prohibited From Having Guns? If you keep a gun in your home and have an adult living with you, you should know whether that person might be barred from having guns. People covered under federal prohibitions include those convicted of felonies or domestic violence misdemeanors, anyone subject to a domestic violence restraining order (after a hearing), and illegal drug users. California’s prohibitions also apply to people convicted of certain misdemeanors in the 10 years (including a domestic violence crime) and those who are subject to various types of temporary restraining and protective orders, including gun violence restraining orders under California’s “red flag law,” domestic violence protective orders, or anti-harassment restraining orders. (18 U.S.C. § 922(g); Cal. Penal Code §§ 29800, 29805, 29825 (2019).)

Modern Ways to Make a Homemade Gun

While it has always been legal for an individual to make a homemade gun, in practical terms the process has not been so easy. A gun is a highly machined piece of equipment, dependent on precise specifications and materials. Most individuals making firearms at home lack the equipment and know-how necessary to make a sophisticated piece of weaponry. However, modern technology has addressed many of these challenges by offering partial receivers and the ability to make a gun using 3D printing, explained below. While technologically impressive, both methods come with a new set of considerations and concerns, and are likely to be the topic of legislation and regulation.

80% Receivers, or “Ghost Guns”

A gun’s “receiver” is the part of the firearm that houses the mechanical components and projects the bullet. Someone using a finished receiver could assemble a functioning firearm by adding necessary additional parts, such as the stock, barrel, trigger component, and magazine. Because the GCA includes finished receivers in its definition of a qualified firearm, someone purchasing a finished receiver would have to do so from a licensed firearms dealer. In addition, a person purchasing a finished receiver must pass a background check and register the firearm. A finished receiver has a serial number that can be used to trace the receiver to the registered owner.

An individual interested in avoiding a background check and gun registration process can instead buy an unfinished receiver (also called an 80%, blank, or partial receiver) to make a “ghost gun” (so called because it cannot be traced). An unfinished receiver is a partially completed receiver that requires additional tooling to be completed. This kind of receiver is not technically a firearm and falls outside the regulatory scope of the GCA (and so does not bear a serial number). Unfinished receivers are legal to sell and distribute and are widely available online and at gun shows.

Because ghost guns are untraceable, it is impossible to know how many of these firearms have been assembled, sold, or used in violent crimes.

Working with Unfinished Receivers

Unregulated receivers can be converted into working firearms by someone with very basic skills and tools. A purchaser uses a drill press to create holes in the receiver and adds other parts to make a fully functional gun. Finishing kits and how-to guides are extensively available online and through specialty markets. Many sellers host “building parties,” where buyers come together to share tools and expertise and assemble their firearms. Ghost guns created with unfinished receivers range from basic handguns to semi-automatic weapons.

As long as it is intended for personal use, a ghost gun is exempt from federal regulation. Individuals purchasing an unfinished receiver or a kit to complete the assembly of a ghost gun are not subjected to a traditional background check, and are not restricted by criminal or mental health history. Additionally, there are no sales records in conjunction with 80% receivers and as a result, when a gun of this type is used in a crime, federal authorities cannot cross-reference information from stores about buyers. The guns themselves are untraceable because there is no serial number on the receiver.

Attempts to Regulate Ghost Guns

In 2013, a federal House Bill intended to ban unfinished receivers used to create assault weapons failed in its entirety. (H.R. 2910.) California has become the first state to require registration: As of July 1, 2018, anyone who makes or assembles a gun must apply first for a serial number or other identifying mark from the state Department of Justice. As of January 1, 2019, everyone who owned a firearm as of July 1, 2018 or later must apply for a serial number or identifying mark. The law has some exceptions. The law forbids the sale or transfer of a gun registered under these provisions. Violations can be charged as misdemeanors. (Calif. Penal Code Sec. 29180 and following.)

3D Printed Guns

Individuals can also make homemade firearms using 3D printers. 3D printing, also known as “additive manufacturing,” is a process whereby a three-dimensional model designed on a computer becomes a three-dimensional solid object as the printer lays down successive layers of material that conform to the programmed instructions. Gun parts, predominately made of plastic, can be generated from 3D printers.

While unattainable to most individuals when the technology first emerged, 3D printers are now widely commercially available at a relatively modest price. In May 2013, the open source firm Defense Distributed unveiled “The Liberator,” a handgun made entirely from 3D printed plastic pieces (save for a common hardware store nail used as the firing pin), and made the digital blueprints available online. In the short amount of time since then, the technology has improved tremendously, resulting in extensively documented successful gun construction. Similar to their ghost gun cousins, instructions, guides, and highly detailed schematics for how to create a 3D printed gun are widely available on the Internet, generally from anonymous sources; comparably, 3D-printed guns require no background checks, serial numbers, or registrations.

While it is not illegal under the GCA to print and make a gun in one’s home, there is a catch: plastic, the material most 3D printers use to make the gun parts. Because the Undetectable Firearms Act makes illegal any firearm that cannot be detected by a metal detector, every firearm must contain some amount of metal. This means that a plastic 3D printed firearm must have a metal plate inserted into the printed body. Such a requirement is difficult to enforce, however, because these firearms bear no serial number and are not registered. The opportunities to inspect these firearms and enforce the metal rule are practically nil. To learn more about the legality of 3D printed guns, see Are 3D Printed Guns Legal?