“3D printing is a terrible technology for the working components of a gun. There is no tensile strength. It would blow up in your face. You can buy guns in Walmart — they are not a scarce product. And if you want a good barrel you can go and get a bit of plumbing from the store.” – Chris Anderson, CEO of 3D Robotics via Wired
This might be an accurate statement right now, but I don’t think the “printing guns” concerns can be pushed aside so glibly as the technology improves.