3D Printing a Gun, Pt.2

Prop gun
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In a previous blog I wrote about 3D printing a working gun project. In this blog I’ll look at finishing the demo version. I’m 3D printing a PM522 Washbear revolver that can fire .22 LR amo. For this demo, I’m using the 8 shot pepperbox cylinder.


Having seen the gun in action, I have wanted to test the limits of my printer by making one that functions. My 3D printer has returned the favor by making all the parts difficult to assemble. All of the holes have been to tight, and all the other parts have been on the wide end of tolerances.

Time – 3d print a gun

If there is ever a factor in keeping 3D guns from going mainstream, it is the time it takes to 3D print and assemble them. In the time it takes to 3D print the small parts of this gun, a criminal can buy an illegal and working gun on the street.

8 shot cylinder - 3d print a gun

3D printing the 8 shot cylinder.

This demo gun has taken 4 days to 3D print. For my non-firing demo version, it has taken 8 hours of sanding and tooling to get to the point I can assemble it into a prop gun.

Processing – 3d print a gun

The files for the Washbear are designed for 3D printing in ABS, and as such the tolerances are tight.

6 shot cylinder - 3d print a gun

3D printing a spare cylinder. The designer recommends filling this version with epoxy and using metal inserts made from brake lines.

For my demo version, I decided to print in colorfabbXT before I went to ABS. I also printed this version at 25% infill instead of solid to save time.
This tolerance and material difference has become the greatest problem so far in the assembly of this demo gun. Everything has been on the high end of the tolerance, resulting in hours of sanding, cursing and dry fitting.

Undetectable Firearms Act Compliance – 3d print a gun

Prop gun - 3d print a gun

Getting close to a working prop gun. It only took a week. The cover is the purple piece in the grip of the gun.

In the USA, 3D printed guns are covered under the Undetectable Firearms Act . This law requires that any 3D printed gun have a 3.7 oz (105 g) of metal in the gun somewhere to be detectable. It should be noted that this law was passed in 1988 before 3D printing was even commercially available.
In the Washbear legal compliance is done with a compartment in the grip of the gun. The idea is that if you get to a firing model, you put some large nuts or steel rods in this compartment. That compartment has a cover to hold the required metal inside the grip.
As a teacher I’m use to government red tape and bureaucratic waste. The cover for the compartment took 2 hr of sanding and tooling with a hobby drill to fit into to grip compartment. If this cosmetic piece was an indication, the rest of the gun will be a challenge to assemble.
I was shocked that a non-essential and cosmetic part of the grip took so long to fit. The only reason that cover was there was to comply with the UFA. If I was a nefarious criminal using a 3D printed gun, I’d just tape over the compartment hole and forget the required metal. The idea behind 3D printing a gun is to make it totally out of plastic, not deal with laws passed in 1988 before 3D printing technology was commercially available.

Fitting – 3d print a gun

8 hours into this project and I have reached a point where I’ll be happy if I can just get the cylinder to turn. While I did print the internal parts, there is no good reason I can see to put them together for this demo.

Prop gun - 3d printed guns

A fully assembled (semi-functional) demo version of the Washbear revolver.

In trying to fit the trigger into the frame, I snapped the end off. I reprinted two of them, for another 4 hours of printing time.

Fear of 3D Printed Guns

Anyone who fears 3D printed guns should check their priorities in life. This gun has taken almost a week to fit together into a barely working prop.

As much as I like the idea of owning my own firing 3D printed gun, I’m not sure at this point it will even be worth it. If I wanted another gun, I could just go to a pawn shop and buy one faster than the time it takes to 3D print the parts of this 3D gun.
Over all it has taken a week of 3D printing, sanding, and tooling to fit the pieces together. For all my efforts I have achieved a non-firing demo version of a revolver.

I have a newfound respect for anyone who 3D prints a working gun.
3D printed guns are not something that lawmakers and gun control lobbies should fear. Given the time and effort it has taken so far to 3D print the Washbear revolver, I could have built a couple AR-15’s with parts from the internet.

3D printed guns are a thought experiment and engineering challenge. The threat from 3D printed guns is minimal compared to other gun control issues.

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