Charon: A Printable AR-15 Lower With P90-Style Handguard

Redditor Halvors7 has published the printable parts to build his FN P90-inspired Charon AR-15 lower. The Charon features an integrated buttstock, handgrip and trigger guard. The stock is fixed but can be adjusted for length-of-pull by using spacers. The lower even supports a number of P90 style foregrips!


Foregrip alternatives



Length-of-Pull Spacers

Steve Johnson

Founder and Dictator-In-Chief of TFB. A passionate gun owner, a shooting enthusiast and totally tacti-uncool. Favorite first date location: any gun range. Steve can be contacted here.


  • Hmm, that’s pretty sweet.

  • I like it. Would like to see how it feels in hand. That’s going to be pricey.. and hard to find a printer that can handle the size. But print one and then cast it… or print and cast a blend…

  • bapi

    i would like to point out that reddit is not the origin of this. its a guy named warfairy (see logo on gun)

    • BombedCarnivore

      WarFairy is a redditor, and he has other designs to boot.

  • WarFairy

    Just so you know, Halvors7 is not the creator of this design, he is the beta tester and created the reddit threads on my behalf.

    He’s a great friend of mine, and any bitcoin donations will go directly to getting this receiver prototyped and tested. The data he gets will then be forwarded to me to make design changes and further iterations.

    This is still a beta release, but it should work as advertised.

    • Steve (TFB Editor)

      Thanks for the clarification. i have updated the post. Can you get in touch with me, my email is (I cannot see your email address because we use Disqus to handle comment).

    • BombedCarnivore

      You’ve been busy man. Don’t forget us at 1911TT

      • As just an observer, might I suggest looking into adding a spare mag holder in the butt stock? I think it could not only add to the firepower, but also the balance of the rifle. Just my two cents, awesome design though!

        • KB3UBW

          He mentioned on the reddit post that that might happen in the future, once he works out all the kinks in the design. If you dont want to wait, somebody posted a quick tutorial on how to do it, in the reddit thread

    • FourString

      Keep up the work, this is brilliant.

    • jamezb

      I, LIKE IT! Aside from the obvious incredible printable aspect, for the non-printer-equipped, -this attractive, modern, ergonomic design simply needs to be avalible on gunstore shelves as well! I could see this design taking a major bite out of the conventional AR-15 market! Congrats and best of luck…now go get that beauty into production so I can buy one,

      I’d like to see it with a SBR P90-mag upper on it! Talk about a PDW!

  • Gabriel Owens

    i wonder how “balanced” it feels.

  • Yes please.

  • Kralizec

    Alternatively:/k/ makes the firearms blog.

    Regardless, I’m glad someone’s doing DEFCAD/Def. Dis.’s work, carrying on the 3D printer fad/movement

    warfairy fuck yeah

    • Steve (TFB Editor)

      I don’t read /k/ as much as I should be 🙂

      Some pics from the /k/ thread on this subject…

    • Steve (TFB Editor)

      I don’t read /k/ as often as I ought to 🙂 Some picks from the /k/ discussion on this topic …

  • JT

    Aren’t pieced-together designs actually more resilient when we’re talking about 3-D printing? The strength of steel is not there, so flexibility and stress distributed over more surfaces seems important

  • Reaper

    Didn’t know TFB turned into a repost of Reddit…

    • Not a bad arrangement. Means I never have to go to Reddit to see gems similar to this.

  • T3CH

    I can’t be the only one wondering what that would look like with a short barreled AR-57 upper on it can I?

    • sianmink

      it’d be pretty neat.

    • Black_Viper

      I’m right behind ya on that. I’ll be doing it fo-shoo

    • FourString

      Third party P90, good idea.

    • All it really needs is the shell of a Magpul quad-stack as a brass catcher, and I’m in.

      On second thought, with the Defcad printable magazine blueprints it should be easy to whip up a printable brass catcher.

  • Fuddleton

    Now this is a game changer, pretty much fixes all receiver integrity problems from old designs.
    Instead of replicating the old AR lower design, their working around the problems of the material to deliver this. Wonder how well the buffer tube will hold up though.

    • sianmink

      If it were my design, I’d set it up to hold a standard carbine buffer tube within.

      • JumpIf NotZero

        No. Anyone that suggests a fixed stock get a carbine buffer and spring have absolutely no idea what they are doing and should stay away from guns. I looked over the reddit and can’t see if this is A2 or carbine but it ABSOLUTELY should be A2 if it could at all be made to fit (looks like it).

        • Cymond

          Tell that to CavArms/GWACS. The original Cav-Arms lower used a full-length rifle buffer system, but it had LOP significantly longer than an A2 stock due to the extra reinforcments needed for polymer stocks. (14.5″ LOP) They eventually offered a service to shorten the stock and modify the integral tube to use a carbine buffer system. Later versions used a A1 LOP and carbine-length buffer system.

          • MilesBelden

            Exactly, while a rifle buffer tube “could fit” it may not be the best choice for durability testing. Saying anyone that would choose a carbine buffer system in a fixed stock assembly is just ignorant. I would love to see your FEA results on this stock JumpIf . . .

  • sianmink

    Gets around many of the weaknesses of the standard AR lower in polymer, and it looks very beefy in the right spots.

    This would look pretty sweet with a shorty 5.7mm upper.

  • Timothy Tankersley

    This on a AR 57?

    • Yes, needs an AR-57 upper and the detachable forward grip for maximum uncanny valley.

  • Stephen Lucas

    Hmm… This looks to me like a genius solution to the California AR problem. Perhaps not its intent, but it would fit the niche, if I understand their laws right.

    • Cymond

      Nope, doesn’t help. Thumbhole stocks are classified the same as pistol grips and telescoping stocks.

      • Stephen Lucas

        Oh. Sad. Thanks for the tip, though. At least I don’t live there.

  • jdanna

    Um, Is it just me or is it missing the hole for a rear takedown pin?
    It looks like it has a tiny pinhole where there should be a much bigger one

    • Patrick

      It’s there, slightly forward and below that small pinhole(see first image). Man, if DefDist had thought of this, they could have saved two months instead of reinforcing the buffer tube tower. I can’t wait to see the beta test.

      • jdanna

        That looks to me like the safety selector hole. That tiny pinhole is in about the right place for the rear takedown pin, just looks to be the wrong size

        • Patrick

          Ah, you’re right.

    • Nadnerbus

      As wide as the receiver wall is there, the pin may not protrude all the way through, but be recessed under that smaller hole.

  • JumpIf NotZero

    The “designers” of those horrible Cali-compliant stocks should print one of these to smack themselves in the head with. Trademark issues aside this is awesomely better idea.

    • FourString

      Problem in Cali is that a thumbhole stock is labeled weapon-of-mass-destruction-evil >.<

  • rjackparis

    Barring the whole 3D printing thing. Am i the only one that would buy this if it was sold from a company? like if new frontier produced these and sold them in the same price range as their regular polymer upper?

    • Cymond

      I’d love it if an experience polymer company produced this design, or the updated designs shown in another TFB post. Magpul? No, they constantly design guns but never build them (Masada, FPG, PDW). I think GWACS already has the equipment, expertise, and FFL to build them.

      • rjackparis

        More like new frontier army. I’d pay for the extra cost. as long as it was under 200 for a fully built lower.

  • Clodboy

    I see somebody’s been playing Metro 2033.
    Although in the game it’s an AK74 that’s fitted with the P90-style stock….

  • Alexander

    Not a bullpup? Well, at least it’s a solid start.

    • kalashnikev

      Nobody wants a bullpup. FN is pulling the FS2000 and the Tavor will eventually be the same fad that the new AUGs were. They will always be around as hobby guns for the gottabedifferent crowd, but I don’t think they will ever have great commercial success.

      • Zepe

        They already have commercial success, AUGs used by several countries, new version of it is being tested right now by the Australian Army, the Tavor was adopted by the IDF as main rifle, British Army uses the SA80 as main rifle and squad automatic weapon, FAMAS is in use by French army, they plan to replace it but with another bullbup, the AUG.
        Why would they not be successful? They offer the same in a smaller package.

        • kalashnikev

          With the exception of the AUG, those are all designs cooked up so they could have a local industry. Any professional user with a choice carries an AR-type. Why handicap yourself with a bullpup rifle?

          • snmp

            Simply for have 20″ barrel with 5.56 NATO with Rifle smaller than M4.
            Infact the real question is: why pay full price an rifle when US Govenement provide free an M16 or an M4?

          • kalashnikev

            So they could have a local industry. The same reason we manufacture all our weapons on American soil regardless of their origin.

          • Chrome Dragon

            Because I like back-heavy ergonomics. They just point more naturally for me, I find them easier to shoot accurately when most of the weight is on my shoulder rather than on my support hand, which can concentrate on making fine adjustments.

      • Don’t forget the Kel-Tec KSG and RFB, both of which sell as fast as they can be made.

        Also, Singapore has a bullpup in the Singapore Kinetics “SAR 21” (Singapore Assault Rifle, 21st Century) – which includes an integral optic and laser (both IR and visible red, I believe).

        • akmarksman

          because building 10 long guns a year really strains Kel-Tecs production line.

          • Chrome Dragon

            I really do wish they could crank them out fast enough for my tastes. I kinda want one of each of their long guns, but I’d be much more excited about the SU-16 if it also came in bullpup – it’s already much lighter than most ARs, and I’d be ecstatic if it was shorter, too. A designed-in quad rail would be nice, too. I’d even give up the fold-in-half trick for the bullpup geometry.

          • kalashnikev


      • themastermason

        Well not everybody wants the firearms industry and landscape to be just a flat range of AR-15’s, glocks and AK’s. I understand for good reason that a number of things need to be standardized to minimize headaches and allow serviceability but at the same time we need to keep substantial variety in firearms.

  • snmp

    That’s Look like a “Carter Special” (SIFI Stargate SG1) : AR15 Micro Carbine with a Bell & Carlson thumbhole stock

  • Ian

    It’s an improvement, particularly by following Calvary Arms’ understanding of plastics, but it will still suffer from broken pivot pin tenons. I would also not use the printed plastic as the buffer tube (which is carbine length, by the way), as appears to be the intent. If it were me, I would counterbore the front of the opening and insert a standard rifle tube from the front, using the standard buffer detent as its retainer. The recoil spring will destroy the surface of the plastic and the .768 wall at the rear will not handle constant buffer pounding as well as a supported aluminum tube would.

    The P90 aspect of it makes it look appealing, but to me it looks terrifically uncomfortable to grip, what with it’s non-human grip shape.

  • I actually kinda want one. It looks like a director wanted a P90, but low availability forced the props guys to get creative.

    • Cymond

      Actually, Stargate had been using P90s for a long time, and then they started diversifying. Personally, I think the shorty-AR was a great idea for the show. The muzzle blast would be horrendous, but it still beats the P90s ballistics.

  • Nicks87

    Sweet! I love it. Let us know when you get all the bugs worked out and decide to put it into production. If the price is right I think it would sell like crazy.

    • WarFairy

      Free’s good. I like free.

      None of my designs will ever be charged for. All of them will be available on one corner of the net or the other without payment required.

      You just have to print it yourself.

  • Ben Anselmi

    would this work for airsoft

    • Garrett

      If you use a WE or a PRIME spec’d WA platform, then yes it will work.

      • Ben Anselmi

        i have a aeg m4?

  • Ben Anselmi


  • nice