They look like toy guns, are part plastic and resemble LEGO pieces — yet they are lethal. They are 3D-printed ghost guns, and they are increasingly being found in the United States and used in high-profile crimes.

The guns are hard to trace as they are often homemade, without serial numbers. They can be either partially or completely made with components that have been produced as metal or plastic, on commercially available 3D printers.

In December, police said that Luigi Mangione had used a 3D-printed gun in the fatal shooting of United-Healthcare CEO Brian Thompson, the first known assassination in the US involving such a weapon.

In 2017, law enforcement agencies in the US recovered approximately 1,600 ghost guns, according to federal data. By 2022, that number had jumped to more than 25,000 — a nearly 1,500 percent increase. The 3D-printed guns were present in 700 homicides or attempted homicides, The Washington Post reported.

In the US, selling 3D-printed firearms requires a federal license, but no federal law explicitly bans individuals from making or owning them. That includes 3D-printing the lower receiver, the only component that typically requires a federal background check when purchased from a licensed dealer. By printing it at home, individuals can bypass the background check and buy other gun parts, like metal barrels, from regular stores without additional checks.

Some firearm models can be almost entirely produced using a 3D printer.

On Reddit, a 3D-printed guns community with more than 117,000 members, discusses software and computer-aided design, or CAD, tools. While most participants are hobbyists, the community enforces rules, such as prohibiting the sharing of firearm receiver files.

Arrests and seizures related to 3D-printed guns are rising sharply, with nearly 38,000 ghost guns reported by US law enforcement from 2017 to 2021, including 19,273 traced in 2021 alone.

New York is among the states with the lowest percentage of ghost guns traced to purchasers, yet seizures still surged from 100 in 2019 to 637 in 2022, according to data from the US Bureau of Alcohol, Tobacco, Firearms and Explosives, or ATF.

'A piece of plastic'

"We're here to talk about a roughly 1-inch piece of plastic. It looks innocuous enough, a little like a LEGO or a K'nex block. But this 1-inch piece of plastic is killing people," Leigha Simonton, US attorney for the Northern District of Texas, told USA Today.

"Machine gun conversion devices can turn Second Amendment-protected firearms into illegal weapons of war and petty criminals into brutal killers," he said.

Stopping the production of 3D-printed guns is challenging because it's legal to buy the printers and materials needed to create them.

On 3D gun-builder websites, users can easily find guides for building weapons at home, including recommendations for printers, slicer software, filament, and parts-kit vendors.

As printing technology improves, 3D printers also are becoming increasingly affordable. The most popular 3D printer on Amazon costs about $380, with more than 6,000 units sold in the past month.

The printers can also produce other weapons, such as grenades, bombs and switches that convert guns into automatic weapons. A standard 3D printer can manufacture around 100 plastic switches in 72 hours.

A pistol equipped with a conversion device can fire up to 1,200 rounds per minute, faster than the standard M-4 machine gun used by US soldiers, according to the ATF.

"As simple to manufacture as they are quick to install, conversion devices turn regular firearms into machine guns capable of inflicting tremendous harm in a few split seconds," said US Attorney Chad E Meacham.

"Imagine hardened criminals armed not only with pistols, potentially lethal in their own right, but also with automatic firearms rivaling those carried by the US military. These half-inch pieces of plastic are putting our people at risk," Meacham said.

As of November 2024, 15 US states had implemented their own ghost gun regulations, which vary but generally include requirements for serial numbers, background checks for purchasing firearm components, and reporting the production of 3D-printed guns to authorities.

In New York, possession or distribution of a 3D-printed gun is classified as a misdemeanor under state law.

minluzhang@chinadailyusa.com