When Cody Wilson revealed the world’s first fully 3-D printed gun last year, he showed that the “maker” movement has enabled anyone to create a working, lethal firearm with a click in the privacy of his or her garage. Now he’s moved on to a new form of digital DIY gunsmithing. And this time the results aren’t made of plastic.

Wilson’s latest radically libertarian project is a PC-connected milling machine he calls the Ghost Gunner. Like any computer-numerically-controlled (or CNC) mill, the one-foot-cubed black box uses a drill bit mounted on a head that moves in three dimensions to automatically carve digitally-modeled shapes into polymer, wood or aluminum. But this CNC mill, sold by Wilson’s organization known as Defense Distributed for $1,200, is designed to create one object in particular: the component of an AR-15 rifle known as its lower receiver.

That simple chunk of metal has become the epicenter of a gun control firestorm. A lower receiver is the body of the gun that connects its stock, barrel, magazine and other parts. As such, it's also the rifle's most regulated element. Mill your own lower receiver at home, however, and you can order the rest of the parts from online gun shops, creating a semi-automatic weapon with no serial number, obtained with no background check, no waiting period or other regulatory hurdles. Some gun control advocates call it a “ghost gun.” Selling that untraceable gun body is illegal, but no law prevents you from making one.

Exploiting the legal loophole around lower receivers isn’t a new idea for gun enthusiasts—some hobbyist gunsmiths have been making their own AR-15 bodies for years. But Wilson, for whom the Ghost Gunner is only the latest in a series of anti-regulatory provocations, is determined to make the process easier and more accessible than ever before. “Typically this has been the realm of gunsmiths, not the casual user. This is where digital manufacturing, the maker movement, changes things,” he says. “We developed something that’s very cheap, that makes traditional gunsmithing affordable. You can do it at home.”

Wilson's goal of enabling anyone to privately fabricate an untraceable gun is part of a larger anarchist mission: To show how technology can render the entire notion of government obsolete. He's spent the last two years developing firearms designed to be printed as easily as ink on a page, neutering attempts at gun control. "This is a way to jab at the bleeding hearts of these total statists," Wilson says. "It's about humiliating the power that wants to humiliate you."

More Threat Level:RAM Scrapers: The Sneaky Tools Behind the Latest Credit Card HacksThese 3-D Printed Skeleton Keys Can Pick High-Security Locks in SecondsHow to Use Your Cat to Hack Your Neighbor’s Wi-FiDefense Distributed's controversial creations have included 3-D printable plastic magazines and lower receivers for AR-15s as well as an entire 3D-printed pistol he called the Liberator. But he says his switch from 3-D printing to CNC milling metal makes the ubiquitous creation of usable, lethal weapons one step more practical . “3-D printing [guns] was about signaling the future. This is about the present,” he says. “You can use this machine today to create something to the standards you’re used to...The gold standard of the gun community is metal.”

>That simple chunk of metal has become the epicenter of a gun control firestorm.

In fact, the process of legally milling a metal lower receiver is easier than it sounds. Using the Ghost Gunner to carve a lower receiver from a raw block of aluminum would be a lengthy, complex process. But the firearm community has long traded in so-called “80 percent lowers,” lower-receiver-shaped metal pieces that sell for as little as $80 and are roughly 80 percent finished—They only need to have a few holes and cavities milled out to become the body of a working gun. The bureau of Alcohol Tobacco and Firearms has defined that 80 percent line as the closest an object can come to a regulated rifle without legally qualifying as one. But precisely finishing the last 20 percent of a lower receiver has still required access to a milling machine that typically costs tens of thousands of dollars.

The Ghost Gunner, which measures about a foot in each dimension. Defense Distributed

As with 3D-printers, however, CNC mills are quickly moving from the realm of industrial manufacturing to affordable, personal devices. Desktop CNC mills like the Shapeoko and the Nomad cost just thousands or even hundreds of dollars. The Ghost Gunner was built with $20 open-source Arduino microcontrollers, a custom-designed spindle (the head that holds the drill) and a steel carbide bit. Defense Distributed's machine can't carve pieces as large as its competitors, but its small size makes it more rigid and precise, allowing it to cut an aluminum lower receiver from an 80 percent lower in around an hour. That's a task Wilson says would still be impossible with today’s cheapest hobbyist mills but doesn’t require five-figure professional tools. “We’re making this easier by an order of magnitude,” he says.

Subversive ambitions aside, Wilson doesn’t hide the fact that the Ghost Gunner is also a money-making project. Unlike Defense Distributed’s 3D-printing projects in the past, Wilson says selling its own CNC mill offers his group a way to fund its activities. He considered offering pre-orders of the device through an Indiegogo or Kickstarter campaign, but both sites’ terms of service don’t allow the sale of weapons or tools for making them.

Since he first launched Defense Distributed in 2012, Wilson has demonstrated a knack for throwing technological gasoline onto political fires, from uncontrollable 3D-printed guns to Bitcoin money-laundering software. His latest creation promises to be equally controversial: He’s releasing the Ghost Gunner’s on the heels of a debate in California over a state law that would ban the manufacture of all guns without serial numbers. The bill, widely known as the “Ghost Gun ban” and introduced by Los Angeles state senator Kevin de Leόn earlier this year was designed to criminalize either 3-D printing or finishing an 80 percent lower without a government-assigned serial number in California. The legislation passed California’s senate and assembly, but was vetoed Tuesday by the state's governor Jerry Brown, who wrote that he "can't see how adding a serial number to a homemade gun would significantly advance public safety."

>"Our strategy is to literalize and reify their nightmare, to give them the world they’re talking about."

That veto represents another setback for gun control advocates like state senator De Leon who have warned of the dangers of the homemade lower receivers. “New technology that makes manufacturing guns available to the general public raises questions about whether homemade guns are made by dangerous individuals [like]...criminals and the mentally unstable,” de Leόn said in a press conference last January. “The threat is real. We’re beginning to see an emerging industry and market for ghost guns...No one knows they exist until after a crime has been committed.”

In fact, police believe that an AR-15 built from an 80-percent lower was used by 23-year-old John Zawahri last year to kill five people in a rampage through Santa Monica before he was himself killed by police. Zawahri had a history of mental illness and had previously been denied a license to buy guns; The semi-automatic weapon he assembled from the bootleg lower receiver and parts ordered online was also illegal in California.

A milled AR-15 lower receiver with the stock, barrel and other components attached. The finished weapon has no serial number. Defense Distributed

In the wake of the governor's veto of the Ghost Gun ban, Wilson’s CNC mill could make untraceable guns all the more accessible. And as the video above shows, Wilson isn’t shying away from that face-off so much as directly confronting gun control advocates. He's gone as far as applying for a trademark for the term “Ghost Gun," a move that could limit how gun control advocates are legally able to use it.

“This wouldn’t be worth doing if Kevin de Leόn didn’t know about it,” Wilson says. “What excites me is giving this world to the politicians. Our strategy is to literalize and reify their nightmare, to give them the world they’re talking about.”

And if, as in the case of John Zawahri, his milling machine is used to create uncontrollable weapons that result in real violence? Wilson stands by the answer that he’s given to that question when it was asked of his 3-D printed guns: That the potential for violence is part of the price of freedom. “I believe it’s in the stable of popular rights afforded to the people, a republican ideal consistent with civil liberties,” he says.

“You can have an unserialized toothbrush, and you can have an unserialized rifle,” he adds. “This is important to me. The untraceable firearm is my stand.”

More Great WIRED Stories