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Edit: Just before the publication of this article, Defense Distributed voluntarily removed the designs for the Liberator from their website, at the request of the Department of Defense.  In my opinion, this is Defense Distributed getting the legal fight with the government it was spoiling for.  More on that to follow.

Hello again world.  How are you today?  It's been a while since I last posted, mostly due to school.  Good news is that I had an awesome semester and worked on some very cool projects.  A little polishing, and I'll happily show them off here.

One of the things I've been very intimately involved with this semester is 3D printing.  Consequently, I have some thoughts to share on Defense Distributed, which is aiming to make a 3D printed firearm.  More specifically, I have thoughts on their 3D printed firearm and how much it does - and doesn't - change the security playing field.  I also have a few thoughts on the attitude and approach of Defense Distributed.

I'm going to split this post into two sections.  First, a discussion of 3D printed firearms, and the legal area around them.  Second, a discussion of Defense Distributed.

Part the First

Defense Distributed Changes the Game...

Defense Distributed has created, printed and fired an almost fully 3D printable firearm they call the Liberator.  Additionally, they have uploaded the plans online. The firearm is not fully 3D printable - they use a nail as a firing pin.

Before we get into how this changes security, lets cover the security game.  The security game is really a tower defense game.  You have two players - an attacker and a defender.  The defender controls some target (classically, the other side of the screen) and attempts to prevent the attacker access to the target.  The attacker attempts to get as many of his or her minions through to the target as possible. 

In the security game, there is not simply one route to guard, but many.  And rather than play in rounds, the game in continuous.  Furthermore, the attacker wins by getting any one of his/her minions through to the target.  This is, quite obviously, a massively unbalanced game, in the attacker's favor.  The only way the defender has a chance of winning is if the defender (e.g: the government of the United States) has immensely more resources than the attacker (common Joe with a weapon).

Defense Distributed and the Liberator change the security game.  In the past, the defender counted on firearms being giant hunks of metal that are easy to detect and trace to an individual - no longer.

... But not THAT Much

Every news story, every reaction, every comment I have seen on DD's firearm misses one critical point.  The Liberator still fires metal bullets.  That is, the weapon may be undetectable, but the ammunition is not.  From a security point of view this means we don't have big easy-to-detect chunks of metal to look for on metal detectors.  Instead, we can look for little pieces of metal optimized for riding an explosion to near-supersonic speeds.  We already don't allow ammunition into places we don't allow firearms.

Lets consider the new situation.  I have an undetectable firearm in a secure area.  But no ammunition.  So what can I do with my weapon?  I could threaten someone with it.  However, I'm in a secure area.  Showing my firearm without intent to fire it will bring a whole lot of security towards me.  Security forces will have functional, metal, multi-shot, LOADED firearms.  That won't work out well for me.  I could... Nope.  I ran out of ideas for ways I could use a firearm without showing it and without ammunition.  I'd love to hear any you've got.

Now the defender in the security game is attempting to prevent ammunition from entering a secure area.  A slightly more difficult task, but certainly an achievable one - and presumably one they're already equipped to do.

Technical Merits

As a knowledgeable amateur in 3D printing and as a (software) engineer, I am able to do a high-level technical evaluation of the Liberator.  In short, I find it massively lacking with problems that are mainly engineering and lack-of-expertise problems.  

First, their choice of materials/printers is sub-optimal.  The firearm they printed is made of ABS plastic.  Less expensive printers than the one they bought are available which print instead using PLA plastic - a harder material - and/or ABS - as they already use.  PLA is admittedly more brittle, which in this case could probably lead to worse catastrophic failures.  PLA also has a lower glass transition temperature - the temperature at which it becomes soft and malleable.  Frankly, I'm not sure how much these matter - I haven't done the math on the thermodynamics of firearms and don't know how much heat will be transferred to the weapon.  However, the use of soft materials in a firearm is probably unwise.  Soft materials are more likely to deform, warp, or suffer a catastrophic failure.  Any of these failures potentially injures or maims the user of a firearm. Defense Distributed showed how dangerous failures could be quite aptly when the second firing of the Liberator resulted in a catastrophic failure of the weapon.  I understand Defense Distributed was somewhat restricted in their choice of printers and materials due to manufacturers refusing to sell them printers.  However, their choices are still remarkably poor.

Beyond the technical constraints, I'm concerned by the lack of engineers on the team.  Not one of the team members is a firearms engineer, mechanical engineer, or even has experience working in the physical world, according to their bios.  Based on their seeming lack of engineers, I am very interested in what their engineering process was.  I hope it wasn't guesstimating - guesstimating is not okay when you're dealing with potentially lethal explosions.  I sincerely hope that they did proper engineering to figure out how thick the parts of the Liberator should be, based on the forces involved in firing.

However, I'm not a mechanical or firearms engineer and I'm unable to do any further analysis.

Legal Issues

The largest barrier to Defense Distributed actually producing the liberator has been legal challenges.  They have faced everything from questions from the US government over whether they would need a firearms manufacturing license to printer manufacturers declaring Defense Distributed to be in violation of leasing terms and seizing the printer.  However, Defense Distributed has quite adeptly dealt with every legal challenge.  

What challenges will they face now?  Beyond the obvious laws aimed at making them go away, the biggest challenge is likely to be liability for use of their designs.  Very informally, I asked a lawyer friend of mine for an off-the-cuff response.  He said that, if he were to go after them, he would attempt to make them responsible for others using their designs using civil, not criminal, law.  Under a theory called market-share liability, any 3D printed firearm would be their responsibility, as they would be the only player in the market.   They would therefore be liable for any damages caused by one.


Defense Distributed has created and fired the world's first 3D printed firearm.  This accomplishment required more determination, persistence and legal acumen than engineering cleverness.  It changes the security game - now the defender looks to prevent ammunition, rather than weapons entering secure areas.  3D printing a firearm is undoubtedly an important landmark but is not as large an issue for security as many present it.

Part the Second

Defense Distributed is entirely the wrong group of people to design and distribute a 3D firearm.  Furthermore, they're also taking the wrong approach.  I touched on some of this slightly earlier when I spoke about there not being a single engineer on their team.

Defense Distributed doesn't have a single mechanical or firearms engineer listed on their team.  They don't have anyone listed with knowledge of 3D printing.  They've got a law student, a philosopher, a couple of computer people, and a medical student.  Where are the engineering experts?  This team allows them to quite adeptly deal with legal challenges.  However, it is surprising that they've managed the engineering challenges without injuring anyone.

Beyond the apparent lack of relevant background knowledge, I am concerned about their approach.  As I see it, Defense Distributed is made of true believers who drank their own kool-aid.  True believers accomplish quite a lot through not believing in giving up.  However, true believers is that they stop being able to see sense.  They don't consider what happens if they don't win.  And they definitely don't plan for it.  For the sake of the rest of us, I hope Defense Distributed isn't true believers or has someone close that they trust to moderate them.  Otherwise, I am afraid they'll end up like poor Enjolras - trying to raise an army for revolution and watching the whole thing fall apart around them.

The risk of them losing the fight they've picked extends to the rest of us in 3D printing.  Defense Distributed is shaping the public perception of 3D printing.  If their outcome is negative, I'm afraid they're leading us into the world of Charles Stross's Rule 34.  Every 3D printer in this world must have software in it to prevent the printing of copyrighted designs.  A situation like this - where 3D printers have been shown to manufacture dangerous objects and many are calling for bans on the printing of certain designs - is the perfect way for restrictions like this to enter.  The path from here to Rule 34 is simple.  First, the law requires that any 3D printer sold be unable to print a weapon.  Then lawmakers start to hear about copyright violations, so they add a requirement to prevent the printing of copyrighted designs.  This is a very real slippery slope - it isn't far from preventing one kind of crime to preventing another.


I am worried Defense Distributed is entirely the wrong people to be embarking on a project 3D printing firearms.  In general they lack engineering expertise, though they are very able to deal with  legal challenges.  I am worried that Defense Distributed are going to be the reason legal restrictions on 3D printing exist.  In my opinion, such restrictions will ruin the potential of 3D printing in many ways.

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