Previous Post
Next Post

Given all the OMG gun control hubbub surrounding the 3D printer AR lower project, you’d think the guys could buy a wind sock for their microphone during its initial live-fire outing. Then again, Alexander Graham Bell’s first words on a telephone instructed his assistant to hang up. The not-quite-ready-for-prime-time-printers at Distributed Defense have some sage advice for those attempting to replicate their little feat. “Test firing a printed (ABS-like Objet photopolymer) AR receiver in 5.7x28FN. Lower max PSI than .223, but broke the buffer tube ring within six rounds. We do not recommend printing a lower receiver for a rifle setup until the file can be further reinforced.” Damn! Now I’ve got to find something new to do this weekend.

Previous Post
Next Post


  1. Here’s what I would do. Take their design. Add composite reinforcing (kevlar or carbon fiber with epoxy) angling forward and down to strengthen that stress point. Then shoot the heck out of it again until another point fails. Then reinforce that portion. Rinse and repeat. Once you’ve identified all the weakest points you can do your redesign of the original plastic component incorporating all of it. Honestly, anyone that is willing to go through the trouble of printing a lower and assembling it into a working firearm would have the resources to reinforce it to make it work if tomorrow we have a new widespread Katrina situation. I applaud the guys developing this and like everything nowadays they will eventually get it figured out.

    • Don’t forget the bailing wire in case the pins fall out or your retaining pin for the firing pin falls out!
      Oh and it has to be camo’ed duct tape or it won’t work on a redneck fix it project!!

  2. Seems like a good start, but I am not too sure how sharp these guys are. Test firing a printed lower right next to my face is not a happy-making idea to me. I’d have to clamp that to a bench and fire from well clear, because I don’t like the idea of plastic in my face.

  3. That was… Disappointing. I was actually looking for a test like this this weekend to no avail. I guess I know I can cancel my order for a 3D printer for now.

    On a side note, I think that they are approaching this the wrong way. While making an AR lower from existing schematics may be the easiest way (though judging by these results, maybe not?), the design was based on the tensile strength of metal. Until printing materials are much improved and strength is comparable to the same thickness of metal, completely redesigning the lower to specs that can take the torque and force of the round while maintaining compatibility with existing parts (just not necessarily the exact appearance) of an AR is necessary.

    Who cares if its goofy looking or more bulky than the original, if it works it works. For the intended purpose of a rebellion weapon that’s easily made, that’s all that counts. Also, that way people without access to high strength materials (say, throught government restrictions to civvies in the future) would still be able to manufacture them.

    TL:DR- defense distributed should make their own design for a lower that accounts for the low strength of 3d print plastics while retaining parts comparability with ARs. Ditch the spec demensions and add more material.

  4. You can’t photoprint plastics around an internal reinforcing frame, because the reinforcing frame will shadow the photopolymer behind it and ruin the print.

  5. There are some printers out there that will print metal, but they’re probably way more expensive.

  6. I rest my case. Lucky no one was hurt illustrating what myself and many others here and elsewhere were trying to explain.

    Its easier, cheaper, more practical, and safer, to just mill the damn thing – and it takes not more expertise that 3D printing, provided you have the appropriate files and equipment.

    • It takes quite a bit more expertise. CNC milling isn’t as push-button as 3D printing. Unless you’re dealing with a high-end CNC setup with custom fixtures, you’re going to have to do some work indicating the part in and touching off tools to load up the mill.

      None of that is necessary on a 3D printer.

        • Well, if you really want to know:

          – you can find VMC’s in the used market from $10K on up. Old Fadal VMC’s are quite economical, parts are plentiful and they work. You’re going to be loading your workpieces by hand, into multiple vises or fixtures, indicating in your tools by hand, etc. This is where industry was 15 to 20 years ago.

          – new, modern VMC’s or HMC’s with all the latest probing systems will start around $60K and go up towards $250K. This is for big-time production of one AR lower after another… you just load forgings or blank pieces of bar stock into the fixture or tombstone and mash your finger down on the green button.

  7. Or you could just buy a bench top cnc mill and machine a new lower….. and upper, and buffer tube, etc.

    • That’s not Defense Distributed’s goal though.

      They want to modify the design, dumb it down, bulk it up, until they have something that can be printed out in a rip-rap, which is a 3d printer made by another 3d printer. Then the tech will be essentially free.

    • As soon as I read the post, I remembered someone 6 months or so ago saying it would crack at the buffer tube. Couldn’t remember who. Good call sir.

  8. Only a matter of time until it’s possible. These copiers are very new. Kind of like ditto machines. Eventually they will have ones that will seem like lazer jets compared to the ones of today. Whether you will be able to buy one without tremendous regulation is another story.

    • They are, and the 3D printer that produced this much-talked-about lower was at the low end of the market.

      People seem to be in two camps – the camp that pooh-poohs this as pie-in-the-sky technology (“It’ll never work”) and the camp that thinks the “print-your-own AR” is just around the corner.

      The truth is off in another quadrant of the issue grid. First, there are 3D “printers” that will print parts out of metal. There are 3D printers that will print pretty strong results out of metal – the process is known as “direct laser metal sintering” and it’s at the bleeding edge of medical device production. The machines are out of a couple companies in Germany, and the technology is wickedly expensive… but it does work and it enables some very interesting things to be done in medical devices and joint replacement parts.

      Second, people need to understand that, just as CNC technology has largely supplanted the old manual machining in manufacturing, the clear, unequivocal trend is towards “additive machining,” of which 3D printing is one part. Many gun manufactures are even now using MIM (metal injection molding) technology to get parts for lock works that are already within a thou or two of final dimension, need only cursory polishing and cost so much less than machining the parts out of bar stock (even on a CNC or EDM machine) that there’s no conversation about these issues now – it’s MIM or get out of the business.

      3D printing is the next new revolution in manufacturing because it’s more cost effective. When you’re CNC’ing bar stock or forgings into gun parts, there is tremendous waste of the raw materials – and that’s an overhead for the gun maker – especially when we start talking of some variants of stainless steels.

      • Well the “waste” is often compressed into pucks and sold to foundries. So it’s not completely wasted.

        • True, true… but (I’m chuckling here)… you as the shop owner don’t get anywhere near the price you paid for that material as scrap as when it came into the shop.

          You’d think that, sorta like recycled aluminum cans, you’d get a pretty good price for sorted 6061 or 7075 aluminum chips in a big container, right?

          Not so much.

    • 3D printing, better known in the old days as “stereo lithography” was created back in 1984.

      In the late 80s early 90s machines were large, expensive and not terribly practical for most apps. But since 2000+ 3D printing is pretty much everywhere.

      Commercial desktop machines are quite reasonable, especially thermoplastic models.

      The stuff that’s rather new (in the last 5+ years) is the metal printers which are generally referred to as Direct Metal Selective Laser Melting, (SLM) or whatever. Long story short, they print in metal. Which would likely print (at least) as high quality as most AR lowers made right now.

      I know someone with one, perhaps I’ll give it a go next time I get out there for biz. I know he can print in 316SS/bronze and 420 SS/bronze. I’m sure there’s other materials available as well.

  9. Ok serious question:
    We know companies, like well everyone make polymer pistols. What is the difference in that compound compared to that of what is in a 3D printer? Also like polymer pistols, many time the slider rail is metal so it is inserted or placed during the production process. Is it possible to do the same with printers?
    The other idea I had, was two fold.
    1. Lets say you use the printer to create the model for the mold. You can then you traditional polymer injection techniques to mass produce the lowers, frames or what have you, and in those instances you then have the option to install things like steel, or what ever to strengthen the object.
    2. Is it possible to use other materials in the printers besides an ABS based compound? This seems to be the stinking point where these things are failing.

    I know their main focus was hit the print button and instant part, but the reality might be that this is simply part of a process, where you build something in a final step. While purchasing blanks from a foundry and milling them yourself is an option, it is also time consuming. There are people who make jigs, and you can do most of the milling on a simple drill press with mill platform, by hand. A low cost CNC minus the cutting bits runs around $5,000 depending on if you purchase new or not.

    • The plastics most commonly used in plastic pistols are somewhat similar, being thermomolding. They are just expensive. They could make this out of Valox resin (the super tough and dense stuff that the balls in mouse were made out of) and be done, but then it would cost a ridiculous amount.

      You could potentially make a metal insert by printing a bed down for it, heating the metal part in a normal oven, then smooshing it into the bed, then printing over it.

      That actually sounds pretty cool… I think I’ll work that into my plastic SMG design, for the firing pin.

    • There are other materials available, but its about $800/gallon and works with machines that are usually around $100-150k. Not exactly the cheapest option, but the tech will get there eventually.

    • Tech is already there to print in metal, been there for a while and getting better every day.

      Look up ‘3d metal printing’ for a sense of how wide the industry is already. Process is called Direct Metal or SLM or different things by different folks. But it’s there, and it works just peachy. Not perfect, but gets better everyday.

    • My thoughts exactly. One failed test is actually GOOD news… means the technology will continue to progress and improve.

    • Exactly.

      The field of additive machining is still rather new. The progress that has been made at the low end of the field is, to me, quite impressive.

      To compare: CNC machines go back to the 1960’s – and they’re just now becoming cheap enough in the low end market or the used machine market that some home/hobby shops can afford them.

  10. Idiot 1: Hey dude, what are you doing this weekend.

    Idiot 2: Nothing, why?

    Idiot 1: Well I made something on my printer that houses a controlled explosion and I want to see if it works. Do me a favor and put it RIGHT BY YOUR FACE until it breaks.

    Idiot 2: Ok, cool, just make sure you film it and put it on the internet.

  11. That’s the quickest conversion from a rifle into a pistol I have ever seen….Is that legal?….Bwhaahhahaaa

  12. Styrene monomer resin/light curing prepregs are currently being used by the US Army and Navy for battle damage repair and commercially in truck repair, pipe joining and sports equipment repair. UV curing has been around forever but was replaced by peroxide.
    “A higher HDT of 82-95ºC (179–203 ºF) can be achieved after thermal post treatment in a programmable oven using different temperature profiles.”

    and for laminations or casting, vacuum assist (vacuum bags) helps the infusion or eliminating air entrapment, can’t do with 3D….comm’l receivers (ATI, plumcrazy, etc.) are injection molded…

    note: Cold Steel used the polyphthalamide “Grivory(tm)” and “Zytel” for their extreme duty trainers, kubotans, etc.

    “Overbuild the ring:”
    thin backstrap there…FN upper limiting with that metal overhang, can’t add plastic at top, and w/ std. upper the charging handle conflicts….use std. 5.56 upper… get side charging bolt handle so can build that up;

    use polycarbonate ($170 versus $14 per 5lb.):

    note on Price:
    5lbs black abs on ultimachine: $96 but only $14 on

  13. The solution seems pretty simple to me: 3D print most of the receiver sans the buffer tube ring, then mill out a buffer tube ring part from aluminium. Then, have the two attach at the rear, via a coarse thread screw, either inserted axially from the rear, or crosswise just behind the rear upper pin.

Comments are closed.