Not that I am eager for the time when everybody can print themselves a gun at home. But I guess it will happen.
Also, I have no idea how to find such a black market. Perhaps asking on Twitter would work? Otherwise I can only think of silk road, the BitCoin market. Never checked it out as I don't do drugs, but perhaps they also do guns?
Not that I want a gun atm, just curious out of principle.
Actually I would like to have a gun in case there is some kind of apocalypse. But I don't want to have a gun around (I think statistics say that you are much more likely to be killed by a gun if you have a gun). There should be some way to hide it somewhere safe :-/