This sort of stuff really gets me excited. Now that barrels are almost hashed out thanks to the wonders of ECM milling technology, it becomes significantly harder to limit the global proliferation of firearms by people DIYing them on their own. Basically, this guy along with another guy I know called Jeff have been successful not only in rifling a steel barrel, but also drilling it completely. The ECM process doesn't care about hardness or whatever, only conductivity as far as milling goes so even 4150 steel is no problemo.
Sure there's still limitations regarding making nitrocellulose propellant, but Jeff has some cool ideas on making a "boom loom" that takes cotton string through an automated process that nitrates it and then washes it, along with other neat things like nichrome electrical primers. I think the future looks pretty bright, don't really need to depend on an incompetent NRA or some men in black dresses if technology marches forward enough.