With the right 3D printer, you can download a semi-automatic weapon—for free. That’s right. Defense Distributed in Texas has designed a 3D-printed “lower” for an AR-15, which is the part of the firearm that contains all of its operating parts. In other words, it’s the heart of the weapon and by law, is what’s actually defined as the firearm itself.

After much trial and error, head of the nonprofit organization Cody Wilson has developed a gun that fires more than 600 rounds. “This is the first publicly printed AR lower demonstrated to withstand a large volume of .223 without structural degradation or failure,” according to Wilson. The only reason the test ended, he continued, was because they ran out of ammunition. “This lower could easily withstand 1,000 rounds.”

More than 10,000 people have already downloaded the lower CAD file. But this begs the question—is it legal?

“There are no restrictions on an individual manufacturing a firearm for personal use,” a Bureau of Alcohol, Tobacco, and Firearms (ATF) spokesperson told Ars. “However, if the individual is engaged in business as a firearms manufacturer, that person must obtain a manufacturing license.”

So how does one go about “printing” their own semi-automatic weapon?

The law student said that anyone with the same type of 3D printer (“SLA resin and P400 ABS on a used Dimension”) could replicate his efforts with “9 to 12 hours” of print time and “$150 to $200” in parts. “We’ve proven that you can build one for $50,” he said, presuming the builder is using lower quality materials. (Dimensions typically sell in the $30,000 range—but Wilson says his results could be duplicated using the less-expensive Ultimaker ($1,500) or Reprap.”

Assuming Defense Distributed’s AR-15 lower costs around $150 to print, it likely won’t end up being price-competitive with other, commercially available polymer AR-15 lowers—a few minutes of Google searching turned up options priced at $135 to $170, depending on the manufacturer.

Of course, lots of 3D printing enthusiasts extol the fact that the price of the technology is rapidly falling—as we reported previously, a California company announced a $600 model last year.

Check it out in action: