One important difference in this branch of rights activism, however, is embedded in the nature of the rights themselves. For obvious reasons, I don't think we're going to see gun control advocates following gun rights activists back to their neighborhoods and burning their houses down (as did in fact happen to one of my neighbors after a lunch counter sit-in here in Wilmingon, NC). Gun control advocates would be more inclined to turn the power of the police and military against their political enemies than to take direct action themselves. It is unclear whether police officers and servicemen would allow themselves to be abused in this manner, however. They are generally cut from the same cloth as common civilian gun owners -- in fact, they are more often than not the same people. So, perhaps there's a buffer of sanity there. Here's hoping.
From what I'm seeing online tonight, it would appear that the service used to offer the 3D printer file downloads balked at this activity and shut down the process. Undeniably, it did offer a new way for people to violate a lot of laws. And it flies in in the face of the values of the overwhelming majority of genuinely hard-core gun rights supporters here in the US -- who genuinely want an effective means to keep high quality weapons away from criminals, incompetents, and the mentally ill (they're just not willing to accept gun confiscation prep disguised as universal background check provisions).
A lot of people are upset about this development -- 3D printer guns -- but I suppose it is an almost inevitable element of the introduction of the technology. It's a bit reminiscent of the incident back in the 1980s in which a rabid gun control advocate -- Charles Schumer, D-NY -- stripped down a Glock handgun and snuck the inert plastic grip frame through an airport security X-ray machine in a lead photographic film protection bag -- then loudly crowed that the government must ban "plastic" guns. Only this time it's an activist from the other side of the political spectrum and the message is more of a finger in the eye of gun control advocates. Yes, yes -- the sky is falling all over again.
First -- a bit of perspective on all of this. Anyone on earth with a bit of mechanical aptitude and a strong motivation can make a firearm out of materials that can be scrounged, using common hand tools. Small quantities of ammuniton bleed out of even the tightest of dictatorships. Alternatively, ammunition can be reloaded or even fabricated entirely by a similarly-dedicated individual. There are places in Pakistan and Afghanistan where people make modern weapons like the AK-47 out of scrap metal with hand tools. So, the question isn't really whether this 3D printing makes personal gun fabrication possible. It's more a question of whether the technology makes personal gun fabrication quick and easy for anyone who can operate common western office tools.
The answer to this is a bit complex. Yes, it does appear that a "zip gun" type single shot handgun can be produced on a 3D printer. However, it's clear that such guns are structurally weak. Materials and design improvements may change this, but it would appear for the moment that this plastic pistol is barely strong enough to survive a few firings. Common hardware store offerings can be turned into much stronger zip guns with inexpensive common hand tools -- and if designed and made reasonably well, they should be highly durable. With a bit of planning and care, they can also be made reasonably accurate.
Currently, a 3D printer costs about 8 thousand dollars -- as much as a decent second hand automobile. I've never even seen one. They're still quite rare. And they're just a moot point, from a practical perspective. I guarantee you that eight thousand bucks will buy you a good gun and ammuntion for it on the black market anywhere in the world today. There probably aren't many places where a black market gun would cost anything near that full 8 grand, either. Japan, perhaps. So, if you're buying a 3D printer to get a gun, you're just playing around anyway.
Of some practical interest is an attempt by the same activist to offer a useable AR-15 lower reciever that can be printed out in plastic. The testing of one of these, assembled into a low-recoil 5.7 NATO - chambered carbine, appears to have resulted in catastrophic failure of the plastic receiver in six rounds. That's an abysmal failure. Again, the materials and/or designs simply aren't up to the job. And in the case of this plastic receiver, almost the entire gun has to be purchased as parts -- making it cost about as much money as a complete weapon. It's the kind of thing that could only be done well in a relatiely open society like the US, where gun parts are generally available. While it is true that a successful lower receiver made on a 3D printer would make circumvention of gun control efforts a bit easier -- if it worked -- which currently it doesn't -- it's still a lot cheaper to do something like make a Kalashnikov rifle receiver out of sheet metal.
3D printing will almost certainly improve in the years to come, but it seems to be a long ways from producing guns better and cheaper than those already hand-fabricated world-wide. This is not a current practicality. It's just a cultural and political battleground.