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We're not afraid of 3D-printed guns -

What do you think? Are you?
Terry Griffis's profile photoPhillip Rumple's profile photoStephen L's profile photoMichael Meyers-Jouan's profile photo
Not yet. The people that will eventually perfect this technology are the people who cannot obtain weapons through legal means. Then it will be time to get scared.
Why the heck should we be afraid of 3D printed guns? I can pick up a Hi-Point pistol for like $150. Criminals have their own avenues for guns. Think much would really change?
I don't think this will be an issue at all in terms of availability of weapons.  Anyone who can afford to keep and supply a 3D printer could just as easily afford black market firearms, or the equipment needed to make a zip gun.

3D printers are expensive.  Particularly ones with sufficient precision to make a theoretically effective firearm.  And while it is expected the price of these will come down in time...

The 'ink' for 3D printers is another story altogether.  Most of these printers 'print' primarily via thermoplastic.  Most plastic is derived from petroleum, which is constantly increasing in price- occasional dips, yes, but an overall steady trend upwards.  As such, even if the cost of the printers goes down, the cost of the 'printing' material will increase.  Significantly, I believe- even if the particular plastics are not derived from petroleum, demand for non-petroleum plastics is going to increase as the supply of petroleum and therefore the cost of petroleum based plastics decreases.

Aside from all that- I'd rather have untried, flimsy plastic weapons in the hands of our criminals than tried, tested, and proven ones any day.
Guns cannot be printed—only parts for guns can be printed.  The barrel of a gun has to be metal; no plastic currently in existence can withstand the stresses of a cartridge exploding within a cylinder.
But it doesn't HAVE to fire a traditional cartridge to function as a gun.  A caseless round propelled by compressed gas could easily work in plastic, while carrying sufficient energy to kill or maim.  A longer barrel and a sabot-style round could allow for similar muzzle energy at lower velocities.
+Kevin Murray And use toxins in the projectiles, so they only have to break the skin to be effective.
As the article says, "It’s the dangers I don’t see that worry me, not the dangers in front of my face."
Certainly, +Kevin Murray, but that's not what all the fuss over "3-D printed guns" is about; when people voice concerns about printing guns, they are almost always thinking of something like a 1911 or Glock (or even an AK-47) that is made of plastic.  The concern is generally not that non-traditional projectile weapons could be made, but that people could print firearms at home.
Honestly the question isn't about the guns, the question is about humanity:  Is humanity ready for the ability to create pretty much anything they can think of, just by pressing 'print' on a computer screen?  Do we seriously think that we are all capable of dealing with the ramifications of this?

It is that question, not the one posed above, that really should be answered.  Guns, weaponry, adult toys, etc, can all be made using 3d printers...what we are going to start censoring hardware now?  Egad, people, let's get real:  The issue isn't the software, or the hardware, or even the item created, it's the people who use it.
At least, this is the case in all of the news articles and blog posts I've read on the issue.  They are all worried about firearms, not other possible projectile weapons.
I thought the issue was in general accessibility of easy to use and lethal weapons.  That's why guns are a problem- they require significantly less training and ability on the part of the user than most other weapons we've used historically.  You can make a bow and arrows out of materials in your back yard that'll be good for a shot or two within the range most handguns are used at, but it takes a lot more skill to use it.  Edit: And strength for that matter.
Federal law defines a firearm as the receiver portion of gun; it's legal, for example, to ship barrels, magazines, etc by mail.  So 3d plastic printing could be used to produce traditional but illegal guns or sidestep federal and local regulations, etc, with the single additional step of buying barrels.  And you can buy barrels online.  
It frightens people so it makes good press. Reality is more complicated and much less interesting to most people so details like "pressure vessel", cartridge casing, primer and powder are ignored. People are infinitely creative and curious about weapons so alternate forms are inevitable.
I think people are more narrowly focussed on firearms (as defined by the dictionary) rather than lethal weapons in general, probably in part because they are the most obvious example of an easy-to-use lethal weapon.  There just isn't the same concern about railguns or high-powered air rifles compared to the worry we see about firearms.
I dunno.  I mean, we didn't arise as the dominant(1) species on our planet for nothing, and we certainly didn't do it with some kind of natural weaponry.

We are absolutely brilliant when it comes to finding ways to kill things.  Brilliant.  Firearms are a big deal due to ease of use, yeah, but we still have a significantly better life expectancy and lower crime rates since the invention of firearms(2) than we did previously.

1- Some may argue this in favor of other species.  No need to nit-pick here, I'm acknowledging this as opinion, if a widely-held one.
2- I'm well aware that there are many other factors than just firearms involved in extending our lifespan and lowering crime rates.  Also, I'm talking averages here- obviously life expectancy has dropped in some places, and similarly crime rates have increased in some places as well.
This is a stupid argument.  3D printed weapons have been around for decades. All guns are CNC milled nowadays, from barrels to receivers. Private citizens who own CNC equipment such as mills and lathes have been making their own 3D-printed guns for a very long time.  The CAD files for an AR-15 are public domain and found everywhere on the net.  If the government is so concerned about private citizens proliferating guns, why not pass sensible gun laws?  It is not supposed to take 10 minutes to buy a gun. It should be one of the hardest, not impossible, things that you do.
CNC mills are not the same as 3D printers.  Additionally, the main concern (at least in this country, where it is easy to purchase a cheap gun) is that these hypothetical guns will be made of plastic rather than metal.
You can't change physics.  There will never be a truly practical fully plastic gun. Where bullet meets barrel will always be metal.  Same with firing pins.  As to CNC mills not being the same as 3D printers, you're wrong.  The only difference between the two is the build material and the tool used to build it. All CNC equipment, from mills to printers, use GCODE for control.  I can take my RepRap and change out the extruder for a rotary tool and easily start milling metal. 
Depends on what value you're supplying for 'truly practical.'

Maybe not practical to fight a war with, but for something intended for one off self defense or, say, an assassination...
So you are saying that CNC equipment extrudes metal into the desired shape?  Of course not—but that's how 3D printers work.
Personally, I‘m for the spread of any knowledge or technology that makes social issues moot. An example: a few years ago embryonic stem cell research was extremely controversial, with persons in the pro-life position (like myself at the time) concerned about the moral implications of destroying live human embryos for scientific experiments. (Notwithstanding that most of those embryos would have been discarded as medical waste anyway.) With the discovery of adult stem cells (which are advantageous in certain practical as well as ethical respects,) together with the advent of harvesting stem cells from umbilical cord blood, the entire issue went from political red meat in the 2004 US presidential election to not mentioned at all in 2008. Regardless of your own views on prenatal personhood, stem cell research no longer requires the destruction of human embryos. Moot point. We moved on.

This is much the same. My own view is I support much stronger gun control. But that opinion was only relevant in a world before the 3D printing revolution. When anybody can print a handgun in their own home, my opinion (and yours for that matter) on the subject no longer counts. The instant the Wiki Weapons Project could distribute physibles over the Internet, whether you see it as the opening of Pandora‘s Box or Prometheus giving Man the gift of fire, the whole discussion of gun control no longer matters. Moot point. We move on.
A gun with a plastic barrel will blow up in your face. The upper receiver which connects to the barrel would melt immediately.  You can't make springs out of plastic.  A plastic gun is a toy, not a weapon.  These guys built a part of a gun that never touches a bullet. This is simply people getting all scared over really nothing. 
I have to agree with +Leodon Spence .  Anything that gets the focus away from the minutiae that people argue over and back onto more relevant issues that affect us all (like foreign and domestic policy) is a good thing in my book.
I love all the pronouncements that plastics won't stand up to the stress and heat generated in a gun. They remind me of all the people who were positive that you couldn't make guns out of ceramic materials, because they would fracture too easily. I wonder how long it will be before 3D printers can work with carbon-fiber impregnated materials?

And the REAL reason that there is a lot of concern about gun made using 3D printers has nothing to do with making it easier for people to GET guns - it has to do with making it easier for people to CONCEAL guns. Most attempts to provide "security" against guns use metal detectors -- which simply don't detect either plastic or ceramic guns.
All this talk about printed guns, what about currency?? If I was a criminal that'd be first thing to be printed!
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