Earlier this year, Cody Wilson, the 25-year-old founder Defense Distributed, a Texas-based group that promotes the use of 3-D printed guns, fired a .380 caliber bullet from a plastic gun called the "Liberator." The shot landed at a dusty firing range in central Texas, but was apparently heard in the halls of Congress.

On Monday, the U.S. Senate addressed those concerns by voting to extend the Undetectable Firearms Act for another 10 years, mirroring similar action last week by the House. The legislation, expected to be signed by President Obama, continues the ban on the sale or possession of firearms that aren't detectable by X-ray machines or metal detectors, a category that could include 3-D printed guns.

“In 1988, when we passed the Undetectable Firearms Act, the notion of a 3-D printed plastic firearm slipped through metal detectors, onto our planes in secure environments was a matter of science fiction,” Rep. Steve Israel, D-N.Y., said on the House floor. “The problem is that today it is a reality.”The law, as extended, requires 3-D guns to have a metal strip that would make them visible to metal detectors. Some Democratic senators wanted stricter controls, including a requirement that 3-D printed guns have permanent metal components.