After just watching another uninformed news segment on 3D printed guns, this time on Sunrise, I felt impelled to post some facts about the reality of such a thing.
Can you actually 3D Print a Gun?
Yes it is possible. Cody Wilson of Defcad.com has released files on the internet for a hand gun which is capable of firing a single bullet. When I say hand gun its more of a zip gun then a fully working fire arm. Zip guns, or improvised firearms as Wikipedia refers to them, can be constructed from every day items such as a simple metal tube, a torch body, PVC tubing or even just a piece of wood. Every one of those items is way more accessible to the average Joe then a 3D printer at this point in time.
Can it really fire nails, shards of glass etc?
NO. Like most conventional firearms a 3D printed gun can only fire a bullet. The bullet cartridge or shell contains the propellant the actually fires the bullet. Like conventional guns, the 3D printed gun swings a hammer (a nail) which contacts the end of the bullet casing, igniting the propellant and sending the bullet forward. A 3D printed gun on its own is not capable of firing anything. The only danger a 3D printed gun posses on its own is if someone threw it at you, and being made of plastic the worst it could do is give you a nasty bruise.