3D-Printed Gun Components – Part 3 by M.B.

(Continued from Part 2.)

Printable Frames and Receivers

These projects generally use a 3D-printed frame or receiver, which is combined with firearm parts to create a finished firearm. Some of these designs can fire over 1,000 rounds without the frame or receiver failing. Projects in this category include a variety of AR-15 lower receivers, such as the UBAR2 and the Hoffman Tactical SL-15, a vast array of Glock frames, like the FMDA DD19.2,  Ruger 10-22 receivers,  and a variety of MAC11/9 lower receivers. There are also projects based on Smith & Wesson M&P pistols, Ruger pistols, Beretta pistols, CETME rifles, the Kalashnikov (“AK-47”), and much, much more.

For many builders, the biggest challenge in a project using a lot of firearm parts is the sourcing of those parts, especially if it’s for a firearm that’s out of production. The media may rant about the availability of “parts kits” or “builder’s kits,” but the truth is that for many firearm projects, the builder must order each part needed and may have trouble finding some parts.

WHAT TO LOOK FOR IN A 3D PRINTER

The first question is: Open Source or Proprietary?  “Open source” printers use common components, so the end user can easily purchase—or print—replacement parts, such as knobs, belts, etc. It also makes upgrading to a better hot end, heat break, etc. easier and less expensive. Open source devices—unlike proprietary products—do not have a planned service life, after which parts become less available.

The classic 3D printer in the gun community has been the Creality Ender 3 (and many other brands made with Ender parts), although that specific printer is now part of an older generation. Your best bet, if you want to go open source, is to do some reading—on Reddit and/or in 3D printing Web forums. There are other printers that may serve your needs better while still being open source. On the other hand, Ender printers continue to sell!

My printer, by the way, is made with Ender parts. It has been very easy to find the few parts I’ve needed for a few small upgrades, and for maintenance.

Software

One recent concern—especially after the public murder of the CEO of United Healthcare by an assassin using a pistol with a 3D-printed frame—has been that the gun ban lobby has been eager to ban 3D printing. As related in a recent article, some software developers are working on programs that are supposed to detect gun parts being made, block the print operation, and may also inform law enforcement. The focus thus far appears to be targeting cloud-based printing management.

No matter which printer you choose, be aware that the firmware running it, and the slicer software producing G-code for it, are critical to your privacy. As of this writing, I’ve heard of no issues with the very popular Cura and Prusa slicer applications, nor with the firmware in common use in open-source 3D printers.

Printer Size

It’s not difficult to determine—before buying—if a printer is large enough for you. Slicer programs can be set by the user to work with any popular printer model, so set it up for the printer you’re considering. If it’s not listed, choose one with the same build space. Now look for the largest object you are considering. Perhaps it’s a receiver or a chassis for a 10/22 or other firearm, or maybe a handguard or a stock. Open the STL file in the slicer and see if it can be moved and/or rotated to be within the build area. Check the instructions to see if a particular part of the item should be uppermost. Don’t forget that you can also raise one end of the object up—taking advantage of the available height in your build space. Just be careful to avoid layer lines running in a direction that weakens the build.

Many projects are designed to be printable on an Ender 3, which has a build space that is 220 x 220mm and 240mm high. Therefore, whatever you decide on, I don’t recommend any printer with a build space smaller than 220 x 220 x 240mm.

Bed-Slinger or Bed-Dropper?

FDM printers have to be able to move the print head—in relation to the object being printed—in three dimensions. Bed-slingers move the print head left and right, on a rail (X dimension) and raise that rail as the object is printed (Z dimension). The print bed moves back and forth (Y dimension).

Bed-droppers have the print head mounted near the top of the printer, where it moves in both the X and the Y dimensions. At the start of a printing operation, the print bed is raised up to almost touch the nozzle. As the print progresses, the print bed drops straight down (Z dimension), while the print head stays at the top of the printer.

Which is better? The bed-slingers weigh less and are more common. The bed-droppers have a frame around them—necessary to enable the movements of the print head and the print bed. This makes bed-droppers heavier and somewhat more bulky, though it can be argued that they’re more rigid. Bed droppers are compatible with cameras, however, because the print head stays at one height at all times. Both types of printer work well, so it boils down to personal preference.

Recommended Features for 3D Gun Part Printers

Heated Print Bed
A heated bed is necessary for some filaments. Filaments that cool too quickly can shrink or warp. Even basic filaments like PLA can benefit from controlled cooling.

All-Metal Hot End
An all-metal hot end can handle higher temperatures than one that contains plastic parts. This feature gives you more flexibility—without having to change out parts—if you want to try filaments requiring higher temps.

Direct-Drive Extruder
Filament is delivered to the nozzle by the extruder. In many printers, the extruder is separate from the hot end (the assembly that contains the nozzle), and a “Bowden tube” connects the extruder to the hot end. This works well, but is not compatible with the higher temperatures needed if you want to print filaments like nylon. On the other hand, a separate extruder and hot end make for a lighter hot end and allow it to print faster. A direct-drive extruder is part of the hot end, and the plastic Bowden tube is eliminated.

Filament Diameter
Make sure your printer is intended for 1.75mm filament. This is the standard in the gun parts printing community.

Filament Types

Knowing which filament(s) you plan to print with can help in making printer decisions. Different filaments require different features, ranging from available temperatures of the heated bed and nozzle, to whether the printer needs to be enclosed with a ventilation system.

The recommended brands and types of filament below are the result of personal experience. Be aware that formulations of filaments can vary between brands. I am running a basic, open source, “bed slinger” 3D printer which would require upgrades to print more exotic filaments, so I’m only recommending PLA and PETG filaments. Your mileage may vary.

Filament Types That I Can Recommend

PLA

Polylactic acid (PLA) is made of natural materials such as corn starch and sugar cane. It’s  very likely the most popular filament today, and this extends to printing firearm parts. It’s strong and easy to print with. All filaments need to be kept as dry as possible prior to printing, but PLA is less moisture sensitive than some other filaments, such as nylon. PLA is reasonably priced and available from multiple sources in an array of colors. Look for names like PLA+, PLA Pro or PLA Tough. I’ve had great results with Polymaker PLA Pro.

Pros: Strong, easy to print with, little or no fumes, no enclosure needed, and economical. PLA (or PLA+, PLA Pro, etc) is the best filament to start out with. A strong argument can be made that it’s the best overall filament.

Cons: PLA deforms at around 60-65° C. (140-149° F.). Items left in a hot car are likely to warp/deform. Items left in direct sun may deform and/or change color.

Recommended brand/type: Polymaker PLA Pro in solid colors (no “silk” or other exotic colors)

Print settings (from Polymaker): Nozzle temp: 190-220° C., Bed temp: 30-60° C. I used a 230° C. nozzle temp and a 50° C. bed.

PETG

Polyethylene terephthalate glycol (PETG) is a strong, naturally clear plastic that is somewhat challenging to print, compared to PLA. It’s more temperature resistant (deformation temperature range is 90-110° C., or 194-230° F.) than PLA, but it may be less shock resistant, though I am still investigating that. PETG also resists solvents, glues, and paints, so choose your color carefully before printing. Like PLA, it is reasonably priced. PETG prints without odors and does not need an enclosure.

All plastics can deform at sufficient temperatures. PETG is okay in a car trunk most of the year, but in direct sun on a dashboard, or on a hot summer day in Texas, New Mexico, or Arizona, all bets are off!  PETG may require a somewhat hotter nozzle temp than PLA, depending on brand, but it’s well within the limits of most printers. It is somewhat more hygroscopic than PLA, so keeping it dry and then drying in a dehydrator or filament dryer for 24 hours before printing is an excellent idea, although Hatchbox—on their website—states that their PETG is hydrophobic (does not absorb moisture), and that no heated bed is required. I still dry their filament and have used a heated bed, with good results.

I had a lot of trouble printing with PETG at first, until I chose a nozzle temperature of 245° C., and slowed the print speed down to a very slow 25mm/s and set retraction to 2mm and “Z-hop” (also called “travel height,” which is a setting that raises the nozzle slightly when it’s moving but not extruding filament) to 0.8mm. I settled on a bed temperature of 65° C., though I have made some successful prints in which I heated the bed only for the first layer. Overall, I’ve had better success with PLA than with PETG. I’m still trying to eliminate some issues with my PETG prints.

One might wonder why I use PETG when PLA is strong and easier to print with. The answer is that I don’t know where I’ll be using the firearm parts I print. Daytime temperatures in my part of the USA are often hot, so I’m testing PETG parts for long-term durability and trying to find the applications where its potentially lower strength is not such an issue. I hope to start testing a PETG CZAR “lower” soon. As the steel upper receiver bears most of the stress, I hope that my PETG lower receiver will last a very long time.

Pros: Strong, little or no fumes, more temperature resistant than PLA, resists solvents, no enclosure needed, economical.

Cons: Generally more difficult than PLA. Hatchbox offers a good range of colors, and I really like their Black and Grey Blue. Other brands of PETG offer an even wider variety of great colors. Not as easy as PLA to glue. Difficult to paint.

Recommended brand/type: Hatchbox PETG

Print settings (from Hatchbox): Nozzle temp: 230-260° C., Bed temp: No bed heating needed. Note that I’ve (mostly) printed Hatchbox with a heated bed, but as always, every printer is its own world.

REMEMBER: YOUR MILEAGE MAY VARY!

Your printer will likely be different, your environment will be different, and at least some of your settings will be different. You may have great results with different filaments and mediocre prints with the ones that I use!

(To be continued in Part 4.)