Direct digital manufacturing company Stratasys may have pulled the lease on a 3-D printer rented out by a group of unlicensed internet gunsmiths. But they're all for making money by printing guns. According to internal sales documents acquired by Danger Room, Stratasys is working with some of the world's top firearms-makers today.

According to those company documents, two "representative customers" for Stratasys's 3-D printing machines include Knight's Armament Company – which makes gun grips and produces its own line of firearms – and Remington Arms, the country's largest producer of shotguns and rifles. A presentation by the company's Direct Digital Manufacturing Group dated to January 2010 also determined that the company's main "selling focus will be to the Aerospace and Defense Markets," and discussed building closer ties to the military and defense industry at various Defense Department, Army and Navy expos, including an "unmanned vehicle conference."

In addition, Stratasys has become a regular exhibitor at the annual Shot Show in Las Vegas, which promotes itself as "the largest and most comprehensive trade show for all professionals involved with the shooting sports, hunting and law enforcement industries." Stratasys is also listed by Shot Show in a January 2012 exhibitor webpage under the categories: ammunition, firearms, "firearm parts/gunsmithing," and "scopes, sights telescopes and accessories."

In July 2011, a forum poster who identified himself as a New England distributor of Stratasys machines, said he had "a database of CAD [computer aided design] 1911 parts available to me," referring to the famous pistol. The poster claimed that "Remington, Savage, Sig-Sauer and possibly others use systems from Stratasys that make parts out of engineering thermoplastics," and also boasted of making a frame and slide for a M1911A1, "a Luger, etc."

But it was a proposed gunsmithing venture that got Cody Wilson in trouble. A second-year law student and director of the Defense Distributed online collective, which intends to print a plastic gun and freely distribute its schematics online, Wilson had leased a uPrint SE printer from Stratasys with a portion of the $20,000 in funds raised by internet supporters. But last week, the company pulled the lease after getting wind of Wiki Weapon, the group's gun-manufacturing and schematics-trading project. Stratasys told Wilson, "It is the policy of Stratasys not to knowingly allow its printers to be used for illegal purposes."

"I don't want to start a spat with them," Wilson says. "But look, Stratasys made a choice, didn't they? They chose a side in the democratization of manufacturing by this little decision."

Wilson maintains he would've done nothing illegal by building a plastic pistol with the printer, and hadn't planned to. But Stratasys pointed to Wilson's lack of a federal firearm manufacturer's license, which he may not have needed. Emphasis on the "may," as the legality involves a complex series of overlapping and (sometimes vague) laws about what you can and can't manufacture in your garage.

There's also a big gap between the kinds of machines Remington can deploy to build components, and the budget printer that Defense Distributed intended to use. Stratasys makes a wide range of systems with different price points, with varying tensile strengths and fidelity in the finished products. A lease on the uPrint SE starts at $299 per month and buying one can cost up to $20,000. But a high-end Stratasys Fortus 900mc (.pdf) can set you back a total price of $380,000, and is also capable of printing a much wider variety of materials up to three times as accurately. The closest comparison to Defense Distributed's (former) printer in the arms industry is a Dimension Elite 3D Printer – spotted in the offices of one gun manufacturer – which starts leasing from a higher $560 per month and costs a total of more than $30,000, but has similar specifications.

It's usually legal to build your own pistol without a license. But if you intend to sell it, then you need to apply for a Title I-class federal firearms manufacturer's license. However, Wilson never intended to sell the pistol. His plan was to simply – and possibly much more worrying to firearms regulators – build a working prototype and then share the schematics online for anyone to download.

On the other hand, a plastic pistol may – the law doesn't exactly account for it – fall under the National Firearms Act's definition of a Title II weapon, which also includes machine guns and easily concealable "gadget guns." You need a license to manufacture those, regardless of whether you intend to sell the weapon or not. There's also the Undetectable Firearms Act, which prohibits guns that can sneak through airport metal detectors.

When contacted on Wednesday, Stratasys provided a statement that read: "We believe Mr. Wilson intended to use Stratasys property to produce a weapon that is illegal according to the Undetectable Firearms Act of 1988 (a.k.a. 'The Plastic Guns' Law) which prohibits the manufacturing or possession of a gun undetectable by airport metal detectors." The statement added, "Additionally, Mr. Wilson failed to respond to the company’s request that he provide a copy of his firearms manufacturers and distributors license."

That act, though, gives an exception for prototypes by licensed manufacturers and weapons built by government agencies. For instance, that means the CIA's secret spy guns are quite legal.

The exemption could also mean Remington could be printing plastic pistols (or close enough prototypes) that can defeat airport metal detectors, but be exempt under the law if they're keeping them in the warehouse. More likely, the odds are that Remington – like other firearms companies – could be using the machines for rapid prototyping of standard gun components. Stratasys machines have been used by Ashbury Precision Ordnance to make a chassis center section for a Tac-50 sniper rifle. Detroit Gun Works used Stratasys machines to build a prototype upper and lower receiver of a .308 caliber pistol. Stratasys even tweeted about it.

Nor is Stratasys the only additive manufacturing company to work with weapons and defense. Competitor 3D Systems has sought to expand into the defense market at the same time 3D Systems's CEO, Abe Reichental, has pushed the printing industry to prevent "unlawful printing of regulated gun parts" before "someone dangerous hijacked this capability to do evil." Think of it like a version of Google's "Don't Be Evil" mantra for the desktop manufacturing industry.

In August, Reichental said companies "should join together so parents don’t have to worry their child might print something illegally and communities don't have to worry that someone irresponsible will open fire with a printed weapon and companies don’t have to worry about counterfeiting and piracy."

But Reichental never suggested that the big firearms manufacturers shouldn't enjoy the many benefits of rapid prototyping and additive manufacturing.