New Scientist said:
HaveBlue did not print an entire gun but only a part called the lower receiver, which serves as a frame for the other components of the gun. This component is the only gun part regulated for sale under US law and as such must carry a serial number - unless it's made by a private individual for their personal use, so HaveBlue is not breaking any laws.
Making gun parts used to be impossible for most people, of course, but computer files for AR-15 components have been available online for some time. HaveBlue claims to have combined a 3D-printed receiver made from hard plastic with parts from an ordinary pistol and successfully fired more than 200 rounds. "To the best of my knowledge, this is the world's first 3D printed firearm to actually be tested, but I have a hard time believing that it really is the first," HaveBlue said.