On Sunday, a West Virginia carpenter who goes by the name "Derwood" released a new video (above) of his "Shuty-MP1" firearm, a small semi-automatic 9mm weapon that is almost entirely 3D-printed with inexpensive PLA plastic. The only parts of the gun that are metal are the steel barrel and springs.

Derwood's gun illustrates the evolution of 3D-printed firearms, which have rapidly evolved in nearly three years since the debut of the simple Liberator and the printed AR-15 lower receiver

"This gun has been a work in process for about a year now," Derwood told Ars. He posted a video of its assembly last week.

"The first model required some welding and machining, and the goal was to keep it simple so that anyone could build it," he added. "It is now to that point."

The Shuty-MP1 appears to be largely based on the AR-15 lower design but with a much smaller upper.

Derwood is part of a group called FOSSCAD , which is "dedicated to the datalove of open source CAD, 3d-printing, awesomeness, and firearms." However he has not yet released the relevant CAD files that would allow anyone to duplicate his design.

The United States Gun Control Act (GCA) of 1968 allows anyone to manufacture their own firearm without a license, but manufacturing such weaponry for sale or transfer does require a federal license.

Derwood told Wired that the Shuty-MP1 isn't perfect; the plastic around the barrel apparently begins to melt after 18 shots if it's not allowed to cool.