Free Men Own Guns, Slaves Do Not ,Yes, it's legal. Read 18 USC, Chapter 44. You do not have to be licensed if you manufacture a gun or ammunition for your own personal use. Similar to say, wine or beer. You can brew your own beer and wine all you want as long as it's for your own consumption (depending on the state you live in). But as far as federal law goes, you can manufacture a firearm without a license. It's perfectly legal to make your own guns. There have been gunsmiths for centuries but what isn't legal is for you to sell those guns to others without being licensed. In fact, if you really want to be cute about this, you can purchse liquid plastics that can make the entire gun and the plastic will be as strong as steel.
Advancing technology is not bad or evil, but people must be prepared to use it responsibly and be aware of the potential dangers new technology will pose. When people know how to use technology and can master it, it can drastically improve their lives. But if people lose control of it, it can be dangerous.