First working 3D-printed firearm built
As the technology improves, 3D printers are being used more and more to create a wide variety of objects, some incredibly useful (like skeletal implants) and some just for fun (like custom robot figurines). Here's another - somewhat controversial - example of just how ubiquitous this technology could become: a working gun built using an AR-15 rifle part made with a 3D printer.
The gun maker, going by the name "HaveBlue," constructed the AR-15's lower receiver - which holds many of the gun's main components, including the trigger assembly and magazine well - using a modified design from a gunsmithing website and an older model Stratasys 3D printer. Since the existing design he started with was intended to be made out of solid metal, HaveBlue altered it a bit by strengthening some of the lug holes and adding a trigger guard. He then printed the design with ABS plastic and used a conversion kit to assemble a .22 pistol.
Amidst protests from an AR-15 discussion board that the part would fail and seriously injure him, he successfully fired 200 rounds using the 3D printed lower receiver without any trouble. To test it further, a metal AR-15 upper receiver was attached and a few shots fired with a higher-caliber .223. So far, the part seems to be holding up well and hasn't shown any major signs of wear.
This certainly isn't the first 3D printed gun part in existence, but it could be the first that's been made into a fully working firearm. What's important to note is that under U.S. law the lower receiver of an AR-15 (or any similar gun for that matter) is the component that is legally considered the "firearm." It's the main part that allows the gun to function, and even has the serial number printed on it for identification. Luckily for HaveBlue, making guns yourself isn't illegal so long as you don't sell or distribute them.
Still, with 3D printers becoming more popular and aimed at home use, a person being able to print their own parts for a working gun - particularly the one component that cannot be ordered through the mail - raises a number of issues. As amazing as it is that a 3D-printed gun could withstand firing a bullet, the potential for someone to build an unmarked firearm much more easily means we could see some pertinent new laws enacted in the next few years.