It's worth noting that with a basic milling machine (about $400) an individual in the U.S. can legally manufacture for personal use an AR-15 lower receiver from

It's worth noting that with a basic milling machine (about $400) an individual in the U.S. can legally manufacture for personal use an AR-15 lower receiver from either a bare or partially machined forging ($50) in as little as a few hours. Some have done the job with only a Dremel or hand drill, making the investment much cheaper. I share this only to illustrate that this technology is not enabling a radical new ability to produce cheap personal-use weapons, but more of an (expensive) prototype evolutionary step in the process. In addition, possibly in contrast to this printed design, a home made receiver that is properly surface-hardened after machining is fully as capable and safe as any other receiver manufactured to the TDP.