A homemade gun is a firearm made by someone other than a licensed firearms manufacturer or gunsmith. These guns can range in quality from crude hunks of metal to sophisticated pieces of weaponry.
Rapidly advancing technology has made it easy to create homemade guns and acquire them. Supplies, how-to kits, and detailed instructions are readily available on-line and at gun shows. Makers don't need a metal shop or even a work bench—3D printing technology makes it possible to create guns with very little infrastructure. See our discussion below on the history of fully functional firearms created with 3D printers.
Yes, there are 3D guns that do indeed work. For years, many believed a working 3D printed firearm existed only in theory. But in May 2013, Cody Wilson, founder of the non-profit group Defense Distributed, released on the group's website video footage of a successful test shoot, as well as the digital design for the first functional 3D printed handgun. Called the "Liberator," Wilson's operational single shot pistol was made entirely of plastic materials (save for a metal nail inserted as the firing pin).
Since the debut of the Liberator, a number of other operational firearms made from 3D printers have emerged. The sophisticated designs attempt to make increasingly stronger and more durable weaponry. For example, in November of 2013, the group Solid Concepts released a handgun made of 3D printed metal parts (as opposed to plastic ones), making the gun better equipped to engage in repeat fire. In November 2014, a machinist from Pennsylvania released plans for a plastic 3D printed firearm with a bullet chamber designed to withstand multiple rounds of firing without cracking or deforming.
To learn about the laws concerning 3D printed guns, see our article Are 3D Printed Guns Legal?
A gun's "receiver" is the part of the firearm that houses the mechanical components and projects the bullet. A finished receiver can be transformed into a functional firearm by simply adding necessary additional parts, such as the stock, barrel, trigger component, and magazine. Federal law includes finished receivers in its definition of "firearm," so someone purchasing such a receiver must do so from a licensed firearms dealer and is subject to a background check and registration requirements. A finished receiver that is legally sold has a serial number that can be used to trace the receiver to the registered owner.
Alternatively, an unfinished receiver is a partially completed receiver that requires additional tooling in order to be functional. A user must use a drill press to create holes in the receiver in order to add other parts. This kind of receiver is not technically a firearm and falls outside the regulatory scope of the federal law. Unfinished receivers do not have serial numbers, are legal to sell and distribute without a license, and are widely available online and at gun shows.
A ghost gun, as the name implies, is a slippery item -- hard to pin down and track. Ghost guns are guns created from unfinished receivers.
The process of converting an unfinished receiver into a working firearm is not an overly complicated process. An operator uses a drill press to create holes in the receiver, then adds other parts (such as the stock, barrel, trigger component, and magazine) to make a fully functional gun. Materials, finishing kits, and instructions are widely available online and at gun shows. Sellers of these unfinished receivers and other parts commonly host "building parties," where buyers come together to share tools and expertise and assemble their firearms.
The primary appeal of creating a ghost gun is that it is exempt from federal regulation. Sellers of unfinished receivers and completion parts are not required to be licensed firearms dealers, and buyers are not subject to background checks or waiting periods. An unfinished receiver does not bear a serial number and the resulting firearm is not required to be registered with any government or law enforcement agency. Without a serial number, the gun is virtually untraceable.
California, however, requires that owners of new 3-D guns register them as of January 1, 2018; and that owners of existing guns register them as of July 1, 2018. (Ca. Penal Code section 29180.)
Homemade guns do not bear serial numbers and, under federal law, owners need not register them. For this reason, it is virtually impossible to keep track of them. In short, no one knows how many homemade guns are currently in circulation.
It is reasonable to speculate, though, that the number of "ghost guns" (firearms created using unfinished receivers) has increased in recent years. The tools required to convert an unfinished receiver into a working firearm are not particularly sophisticated. Both the supplies and institutional knowledge required to develop these guns are widely available online and at gun shows, thereby making these firearms much more accessible than in years' past for the average gun enthusiast.
Conversely, it is not likely that the number of 3D printed guns in circulation has increased dramatically in recent years. While basic 3D printers are certainly more accessible to the average consumer (office supply stores sell printers for several hundred dollars), not all 3D printers have the capability of producing firearm parts; and the ones that do remain prohibitively expensive to most people. The printing process itself is lengthy and complicated, and the finished product won't necessarily be functional. Moreover, the materials used for a 3D printed gun (typically plastic) cannot withstand repeated firings, and the guns are inaccurate and unpredictable. 3D printing is unlikely to be the first choice of anyone looking to produce an effective or reliable weapon.