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3D Printing Bump-Fire Stocks

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Before the horrific massacre in Las Vegas, I, and I suspect most people, had never heard of bump stocks or bump-fire stocks.  As shown below, they are after-market gun stocks that replace the standard stock that comes with semi-automatic assault weapons.  They are made so that there is a gap between the stock and the body of the weapon.  When the weapon is fired, the operator holds the trigger finger in a stationary position.  Upon firing, the recoil causes the body of the weapon and trigger to move backward, compressing the gap between the stock and the weapon.  The recoiling weapon then bumps off of the stock and moves forward, gliding the trigger to the finger.  When the trigger hits the finger, it fires again, repeating the process, which simulates automatic fire, achieving a rate-of-fire of 400 to 800 rounds per minute.  Bump-fire stocks retail in the low hundreds of dollars.

Wikipedia illustration by Phoenix7777.

Soon after the shooting, Congress started talking about enacting a law to ban the sale of bump-fire stocks and the NRA may even support regulating such devices.  On the assumption that anything can be 3D printed, would such a law prevent people from making their own bump-fire stocks?

My Google search of “3D printed bump fire stock” revealed exactly what I expected: a YouTube video of the test firing of a 3D printed bump-fire stock, which was posted by SilkyDionysus4 in April of this year.  On October 10, 2017, gun rights advocate, The Jack News, published an article called “Here’s How to 3D Print Your Own Bump Stock Before Congress Bans Them.”  The article links to a collection of FOSSCAD digital blueprints for a variety of AR-15 parts, including a bump-fire stock.  These digital blueprints supposedly can be used to 3D print a bump-fire stock.  According to the article, this device can be printed in a 3D printer with at least an 8″ x 8″ build chamber.  A smaller chamber could be used if the device is built in pieces.  Although the type of 3D printer is not specified, the bump-fire stock in the video appears to have been printed on a Material Extrusion machine (which some people call a Fused Deposition Modeling, or FDM, machine), which is the most basic and least expensive type of 3D printer, starting at a few hundred dollars.  Bump-fire stocks can be 3D printed in cheap plastic and have no moving parts.

My Google search also yielded a link to digital blueprints for a bump-fire stock posted by Disruptive Solutions in October 2013.  Online forums show that some people in the gun community are shifting into high gear to create and mass-distribute the digital blueprints for bump-fire stocks before any government ban takes effect, and to help others to do so.  I believe the idea is that if the blueprints are distributed widely enough, the cat cannot be put back into the bag.

Bump-fire stock digital blueprints will soon be available on the Dark Web, if they are not already there.  The Dark Web is at least 20 times larger than the World Wide Web.  There is no bag big enough to hold all of the cats that could roam there.

Although the very idea of trying to control the digital dissemination of bump-fire stock design files suggests a lack of understanding of the power of the Internet, anyone who wants to 3D print a bump-fire stock doesn’t really need the Internet at all.  In addition to bump-fire stocks and their digital blueprints becoming available on the Black Market if they are banned, you can design and make your own digital blueprints.  Bump-fire stocks are very simple devices, which almost duplicate the original gun stock.  Anyone with even a little design talent could design a bump-fire stock from scratch (or tweak the digital blueprint for a legal, aftermarket gun stock), using any one of a number of 3D design programs, and could even customize the design.  Then all you need is an inexpensive 3D printer ($500 to $1000) and some plastic filament.  

Although I have read comments suggesting that the high cost of 3D printers will dissuade people from 3D printing their own bump-fire stocks, this is silly.  Anyone who spends hundreds or thousands of dollars on weapons can and will spend hundreds of dollars, if not more, for a machine that provides the ability to make things “away from control.”  Away from control is a concept I pioneered in my book, [easyazon_link identifier=”1516946790″ locale=”US” tag=”3dprint09-20″]3D Printing Will Rock the World[/easyazon_link], and in my YouTube videos, which means the ability to make things without anyone knowing about it or being able to control it.  As I also discuss in my book, the cost of 3D printers can easily be shared in what I call “friends networks.”  Why wouldn’t a bunch of like-minded people pool their resources to be able to make things away from control, or simply to make things so they don’t have to buy them?   And by pooling resources, they could buy a better 3D printer than any one of them could afford alone.

There is also another way to create a digital blueprint without the Internet:  3D scanning.  Here, any one of a hundred inexpensive 3D scanners can be used to scan either a friend’s bump-fire stock or the weapon’s original, legal gun stock.  The scan is then tweaked in a 3D design program to make it a bump-fire stock, which can then be 3D printed.

So this brings me back to the original question:  would banning the sale of bump-fire stocks prevent people from making their own?  The answer:  probably not.

If my underlying message here is not obvious, here it is:  the law enforcement community needs to educate itself on 3D printing and its potential illegal uses, and plan accordingly.


John Hornick, author of the award-winning book, 3D Printing Will Rock the World, offers educational programs to the law enforcement community on the dark side of 3D printing, and on how 3D printing can be used to aid law enforcement.  He can be reached at


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