Downloading a gun design to your computer, building it with a three-dimensional printer that uses plastics and other materials, and firing it minutes later. No background checks, no questions asked. Sound far-fetched? It's not. And that is disquieting for gun control advocates.
Steven Israel, a Democrat legislator, says the prospect of such guns becoming reality is reason enough for the renewal of America's Undetectable Firearms Act, which makes it illegal to build guns that cannot be detected by X-ray or metallic scanners. That law expires at the end of 2013.
At least one group, Defense Distributed, is claiming to have created downloadable weapon parts that can be built using the increasingly popular new-generation of printer that can create 3-D objects with moving parts.
Cody Wilson, a 24-year-old "Wiki Weapons" project leader for Defense Distributed, says the group test-fired a semiautomatic AR-15 rifle - one of the weapon-types used in the Connecticut school massacre. Video posted by the group on YouTube indicates the gun was built with some key parts created on a 3-D printer and fired six times before it broke.
No independent observer verified the test. Federal firearms regulators say they are aware of the technology's gun-making potential but do not believe an entire weapon has yet been made.
Mr Israel says the Defense Distributed effort is chilling.
When the Undetectable Firearms Act was last renewed in 2003, "a gun made by a 3D printer was like a Star Trek episode, but now we know it's real," he says.
Even with gun control pushed to the top of the national political conversation, Mr Wilson, a University of Texas law student, is steadfast about reaching his goal of making a fully downloadable gun.
He keeps three AR-15 parts in his tidy student apartment in Austin, Texas. He and his partners plan to print four new lower receivers - the segment of the gun that includes the trigger, magazine and grip.
Mr Wilson says he was saddened by the Connecticut school attack but protecting the right to bear arms by giving everyone access to guns is more important in the long term. "Clearly what happened in Connecticut was a tragedy," he said. "Still, by affording the Second Amendment protection, we understand events like these will happen."
He says he discussed with his partners whether to suspend their effort, and they all decided it was too important to stop. Mr Wilson acknowledges there still are many technical hurdles to creating a complete gun from a 3D printer.
Advances in 3D printing technology are fuelling Mr Wilson's goal.
The printers were developed for the automobile, aerospace and other industries to create product prototypes from the same hard plastics used in toys.
Prices of the machines have fallen as the consumer market grows, leading to a surge in interest from people in the so-called "maker" scene. More upmarket printers needed to make gun parts cost at least US$10,000 (Dh36,731).
"Nobody right now needs to worry about the bright teenager making a gun on a printer in their bedroom," says Paul Saffo, a Silicon Valley technology forecaster.
* Associated Press