This is huge, and in my opinion is the first nail in the coffin of gun control. This is probably the most significant development in firearms technology since the invention of gas operation.
To give you a little bit of background, the AR-15 consists of two main parts. These are the upper and lower receivers. The upper contains the bolt group and the barrel, and the lower contains the stock and the trigger. Legally speaking only the lower is the firearm. This is one reason ARs are so popular, its really easy to buy an upper, have it shipped to your door, slap it on your lower (with the push of two pins) and change the caliber, barrel length, or even gas operating system of the firearm. ARs are very versatile and very modular.
In the video above, the white part of the firearm is the lower. That is the part that is legally the gun. While I can buy an upper and have it shipped to my door, to buy a lower I'd have to go to a gun store, fill out an ATF form 4473, pass a background check and depending on the state, register the lower. Defense Distributed has figured out how to print this part using a 3D printer.
It has always been legal for a citizen to build their own firearm for their own use. You just could not sell it unless you were an FFL. While legal this practice has been limited to a select few with the necessary skills. But now we can download a simple file and print off a firearm. This is the death of gun control. Gun control depends on distribution control. If you cannot control distribution, then you cannot control firearms.
I will probably discuss this more later, but for now I just wanted to share this extremely exciting development!