Making Firearms with a 3D Printer
Probably one of the hottest topics when it comes to 3D printing, at least when it comes to major media outlets, is printing your own firearms. So, what's the deal?
Well, the bad news is that you can't print an entire, functioning firearm (yet - Cody Wilson, founder of Defense Distributed hopes to make it possible by the end of April 2013). This is because your average household 3D printers aren't up to the task of replicating the parts of a gun that require steel to manufacture, such as the barrel and the bolt.
What you can do, however, is print the part that is legally considered a firearm in the USA - the receiver or frame - and have all the other parts (which are unregulated) shipped to your doorstep without having to jump through any legal hoops, such as background checks. You should check your local laws, but manufacturing your own firearms is perfectly legal in most states of the US, and people have long been taking advantage of this using more conventional manufacturing methods.
You can also print some accessories, such as grips and magazines. So, effectively, you can make a gun without leaving the comfort of your home.
Which printer do I need?
Defense Distributed, the makers of the printable AR-15 lower that's caught headlines, used a Stratasys Dimension series printer, which is a higher-end printer that costs somewhere between $30,000 and $35,000. However, Cody Wilson has said that the lower can also be replicated on much less expensive machines, such as the Ultimaker ($1500-$2000) and the RepRap Project printers (price varies, the basic parts kit starts at $520; fully assembled printers cost closer to $1200-$1800).
Judging from this information we can assume that any 3D printer with an 8" x 8" x 8" printing area or larger can print the lower receiver. The dimensions of a mil-spec lower receiver are 9.025" x 1.500" x 4.090", so in theory, any printer that can fit the part will work. (You'll notice that 9.025" is greater than 8". Cleverly, the receiver is printed on a diagonal, which leaves more than enough room.) However! Make sure that the printer is capable of using the right plastic media; see the next section.
What materials should I use?
Defense Distributed used SLA resin and P400 ABS thermoplastic, which ended up costing around $150 to $200 per AR-15 lower receiver. Reportedly, PC-ABS can also be used with comparable results. Other, lower quality materials can be utilized as well Defense Distributed have proved that you can print a functional lower receiver for as little as $50, but this limits the durability of the receiver. One of Defense Distributed's lowers gave out after only a handful of rounds. Their later models that use higher quality thermoplastics have fired hundreds of rounds in one session without any failures.
Where do I get the designs?
The files are no longer available on Defense Distributed's official page, however they were downloaded multiple times before being taken down. They can most likely be found on other webpages and torrent sites.