Earlier this week, an Austin, Texas-based libertarian group Defense Distributed unveiled a product called the 'Ghost Gunner' --- a machine which is capable of creating untraceable, though legal, "ghost guns."

The first batch - of more than 200 units - of the 'Ghost Gunner' was sold out in the US within 24 hours of its availability. Defense Distributed has said in a Thursday tweet that it will make the 'Ghost Gunner' available for purchase again in January 2015.

The unveiling of the 'Ghost Gunner' by Defense Distributed comes one year after the group sent shockwaves across the world with its creation of a 3D-printed gun that could be downloaded online.

The easy-to-use 'Ghost Gunner' essentially comprises a $1,200 computer-controlled (CNC) milling machine which has to be connected to a PC for creating the lower receiver of an AR-15 rifle --- the gun which was used for killing 26 people in the 2012 massacre at Sandy Hook Elementary School.

The receiver is the part of a 'Ghost Gunner' with which the stock, barrel, magazine and other components - which are widely sold online - are connected.

With Defense Distributed marketing the 'Ghost Gunner' specifically as a tool for milling the lower receiver of an AR-15 rifle, Cody Wilson of libertarian group told Wired magazine: "People want this machine. People want the battle rifle and the comfort of replicability, and the privacy component. They want it, and they're buying it."