Two things should be fairly obvious in a meaningful discussion on gun control.
First: Gun control is possible. To say that people who want them will get them no matter what, is an oversimplification - and not necessarily true, guns being a finite resource, as it were. If the supply is limited, it's limited for everyone.
Second: Banning guns outright, when they've been available for a long time, isn't going to fix anything immediately. As much as social scientists dislike talking about culture as a meaningful factor in anything, I don't think anyone can deny that the US gun culture is different from elsewhere.
How this relates to the possibility of easily and cheaply producing your own gun using a 3D printer is another thing, but it seems to me like if there's a real market for this sort of technology, it's not actually with private citizens. I mean, doing anything in secret that relates to the internet ( which, obviously, is a huge part of this ) is difficult. And you know the laws on something like this would be strict, because there's money involved. If private citizens could print their own guns legally, that threatens the arms industry. The beauty of the corporate state, I suppose.
But if it could be done quickly and reliably, then I can see it becoming something of a revolution for militaries and law enforcement. It changes everything in that case.
Obviously, that's a considerable if - who'd want to trust a printed gun over a proven, manufactured one, if their life depended on it? But if, then it's not difficult to imagine it having a huge impact on the economy. Which is, to say, everything.