Longziz #1: An Interesting Homemade Bullpup with AR-15 Lower Receiver

Longziz purchased his first AR-15 when he was studying in the USA and it inspired him to design his own rifle. A few years later, now studying in Germany, he has unveiled his patent-pending design which he named the Longziz #1.

The rifle is fully ambidextrous. It uses AR-15 lower receiver and trigger group internally. The AR-15 trigger group is connected by a trigger linkage to the forward bullpup trigger (he admits the trigger, like most bullpups, has an awful feel to it).

The triangular Longziz #1 bolt carrier next to an AR-15 carrier.
The AR-15 lower inside the Longziz lower.

Using an AR-15 lower receiver internally is genius. It means he could sell the rifle as a kit (minus the AR-15 lower) without having to be licensed with the BATFE.

[ Many thanks to Jonathan for emailing me the link. ]

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.


  • Lance

    Looks like a fun way to get a unique AR.

  • Anton

    I think it looks great. Yeah, bullpup triggers are quite questionable…

  • Tux

    I like the cheekpiece determining the side of ejection, very intuitive. Someone correct me if I’m wrong, but before it comes to market, won’t he have to modify the housing so a serial number is visible, a la Sig 250?

    • Soless

      Yes. It would be easy enough to mill out a slot to read the serial number.

  • Tomaso

    Nice…real nice..only real problem I see is the magwell…needs to be flared…would be a bitch tring to quickly invert a mag.
    The lever for swapping ejection sides should be a push button..no need to have more protruding parts.
    Overall it’s a great design…I love bullpups.

    • rew

      he mentioned on arfcom he wasn’t too great working with fiberglass, i’d assume a production version would have a flared well

  • Tomaso

    Nice…real nice..only real problem I see is the magwell…needs to be flared…would be a brat tring to quickly invert a mag.
    The lever for swapping ejection sides should be a push button..no need to have more protruding parts.
    Overall it’s a great design…I love bullpups.

  • Too bad he didn’t demonstrate it actually firing to see the ejection.

    • It looks like he doesn’t have it to the firing stage of development, yet. I saw one comment he made in the ARFCOM thread stating that the current bolt is not the final version because it has headspacing issues.

      The impression I got was that he’s still in the prototyping and “fiddling-with-it” stages, and not really even close to having it ready to fire live ammo yet.

  • Jesse

    If he can get it mass produced at the right price it will sell like crazy. I’d say anything less than a $1000 for the whole thing sans lower receiver and it will sell.

  • Nick Pacific

    Looks like a fantastic, marketable product. I hope someone gets hold of this guy.

  • Doug

    Very cool, I’d be interested if the price could be affordable (<$1000)

  • Axel Nordberg

    Is there any way to e-mail this guy? I’m studying mechanical engineering and I’d love to get some more info on how he got this done.

    Very impressed.

    • Soless

      Send him a message from youtube. Too easy.

  • Rusty RAy

    ‘Longziz purchased his first AR-15 when he was studying in the USA……’ I would keep that quiet if I were him. Correct me if I’m wrong, but a study visa does not allow for the ownership or transfer of a firearm. I know when I was there for 6 years on a work visa (paying taxes etc) I wasn’t eligable for transfer……

    But as for the gat, looks nifty. Wonder why somebody doesn’t make a bullpup that ejects down, instead of left or right? That would cure the problem of ambidextrous-ness. And before anybody jumps up and down about hot cases burning the shooter etc etc, there have been a lot of weapons that eject downwards, and very close to the shooters arms too. Most GPMGs do.

    Cheers- Rusty

    • Lost_Thought

      The FN P-90 ejects downward as does the Calico series of guns.

    • ragnarok220

      There is a way to work around it. As long as you have a valid hunting license and a valid visa, you can purchase any long gun (as long as it doesn’t come with a high capacity magazine) you want.

    • GoFightNguyen

      Downward ejection would eliminate the need for a moveable ejection port, but I think the design for a downward ejecting bottom-fed gun would be unnecessarily complicated. It might be worth looking into a forward ejecting design.

      However, as a lefty, I think he has made a very elegant solution to the switchover design.

    • Nadnerbus

      I’m sure it was hard enough to turn the AR into a bullpup, much less changing it to do something like bottom eject. I agree, bottom or front ejection (like the Keltec RFB) are better in a bullpup, but this was probably not the platform to attempt that in. His solution is very elegant and more practical for the design.

    • Doug

      This gent already took care of the ambi issue by a two second process.

      I say he’s just reached the innovation level of FN and Keltec in an otherwise stagnant industry.

    • Dave C

      Hi Rusty:
      Downward case ejection in a bullpup would make any shooting position other than prone a good way to have a shower of hot brass pour down your shirt. As it is, shooting a standard pattern AR left handed can give you some interesting burns.

  • Jeff

    Looks like he took the para ttr / LR-300 concept of a custom, shortened bolt and designed it as a bullpup.
    What I’d like to know is, with that light and short of a bolt/carrier, and with that short of a travel distance, what kind of recoil/buffer spring system he’s using, and the propensity of the carrier short stroking

    • Dave C

      Hi Jeff Zanooda:

      I suspect that that the recoil spring is part of the gas piston/operating rod muck like an AK. The buffer is probably in the usual AR position in line with the bolt group. Which makes me wonder if it would be possible to have a soft recoil design similar to the Ultimax light machine gun:


  • mike

    I’d buy that. I’d love to drop my M16 in there and put a .300BLK barrel in it.

  • Alex-mac

    Regarding the ejection side change feature, perhaps a buttstock that is able to automatically change the ejection side through cheekweld pressure is possible. One problem would be excessive noise in the switch.

    Also perhaps you might find Kel tecs RFB trigger mechanism which isn’t patented, useful in improving the trigger.

    • Matt G.

      The ejection of the ar bolt design is decided by which side the extractor on the bolt is facing. Your “switch” would have to take the weapon and bolt carrier apart and turn it around for you and put it back together. I don’t see that happening.

      • Matt G.

        Nevermind, I’m a retard.

  • Jeff Zanooda

    There does not seem to be nearly enough space for the recoil spring.

    • ThomasD

      Look how much shorter the bolt carrier is. My guess is he’s using a double spring set up.

  • JMD

    That is really cool, especially the way the ejection direction is changed. Clever.

  • amsci99

    ST Kinetics should talk to this guy, probably has a ready solution for their SAR-21, the only bullpup designed under the assumption that everyone in the world is a right-hander. Than again, it’s been more than 10 years since its’ introduction into service and as if they care a damn.

  • Vitor

    As a lefty, I’m quite impressed by how easy it is to change the ejection side.

    And to think all those big companies with hundreds of engineers can’t design a lefty friendy bullpup…

    • foxtrot

      Yeah they can, two bullpups that are left handed friendly: the Kel Tec RFB and the FN P-90.

  • Harald Hansen

    Come on, Longziz, enter it into the US Army carbine competition! 🙂

    • noob

      Interesting. I note that the safety (and probably not a selector) switch is up the front near the trigger as it should be.

      However the AR15 lower’s safety is buried in the stock.

      The ar15 safety actually blocks the sear, preventing the release of the hammer if the rifle is subjected to a shock from the butt.

      The trigger safety in this design only blocks the trigger bar (based on what I can see from the CAD file. I hope that there is a positive linkage (like pinning the trigger bar directly to the sear) to prevent the sear from moving when the front safety is engaged, or you may end up shooting yourself when you try to butt stroke something.

    • noob

      Robarms had a bad experience entering their XCR into a previous carbine competition.

      They were disqualified because they didn’t provide a blank fire device when the blank fire device they used was a standard M16 bfd.

      these competitions are tricky to navigate, even if you have a general behind you pulling political strings.

  • nickro

    I’ll take 2, where do I sign up?

  • W

    Im not a fan of bullpup rifles, though i have to admit, i am pretty impressed. I love seeing innovation like this and independent people thinking outside the box.

  • mr_lorenco

    Here`s a video of the firing mechanism test.Very nifty design,I like it.

    • noob

      thanks for the link. good to see that the work is progressing.

  • Phil B

    Now that is clever, the main issue with bullpup weapons is left handed firing, the UK L85A2 cannot be fired left handed, but this is a very clever way to overcome that issue.

  • Matt G.

    I don’t care much for bullpups but I might have to own one of these if he gets them into production. It just looks so much less rediculous than the other bullpups. I like it!

  • Ronin65

    I used to hate bullpups, I guess it was the look. But after spending a few years in the military, and getting to handle various weapons, I’ve actually come to like them. Not saying I’d give up an M-4 for one, but it would be a great addition to the operators tool box. Nice to handle, great in a CQB situation, and just plain fun to shoot. Would love to see a kit come out.

  • Nadnerbus

    here’s a question: Has he given thought to over-engineering the top of the receiver in case of Kaboom? That was always something that made me a little queezy about bullpup type rifles. Traditional rifle Kaboom is bad enough, but at least the chamber is not pressed tightly against your head.

  • Rijoenpial

    Olá Vítor, tudo bem?

    You seem to have forgotten the most recent and most futuristic looking bullpup: the FN F2000!

    This 2001 FN bullpup chambered in 5.56 precursored the 2010 Kel-Tec RFB chambered in 7.62, with a forward casing ejection tube which prevents casings from ejecting to a left-handed shooter’s face!

    Regarding the cook-off rounds, this F2000 bullpup has a short-stroke gas piston system, while Longziz has a long one, and cook-offs are not a problem in gas piston systems, since all the heat is accumulated in the gas piston area, on the front of the weapon, as opposed to an AR-15 DI gas system one, where the heat and debris are accumulated in the chamber and bolt area…

    Still, this rifle has a hatch where you can safe-check the chamber and clear any malfunctions, to compensate for the forward ejection system…

    But back on topic,

    I like this Longziz design, especially being a homemade one, and love the brilliance displayed on the way he used the cheekpiece on that design… One thing though: the grip is too short and the front end of the upper receiver should be slimmer on the bottom to make it more sleek! Maybe that will be dealt with on Longziz v2…

    Nevertheless, a very good prototype and a great design… I will await the firing tests to see how much recoil the weapon has (one of the major issues in a bullpup design) and its reliability…

    Still, very impressed with this design… Looks very professional and slick… Job well done indeed…


    • DaveR

      What are these “cook off rounds” of which you speak? It has been convincingly shown that in full-auto failure tests of DI M16 systems, the gas tube will fail (melt) before any cook-offs occur.

      (And anyway, the Longziz design uses a piston anyway)

      • Rijoenpial


        There are cases of ‘cook-off rounds’, rounds that explode before the anything else melts…I should note, though, that it may be due to faulty ammo, not necessarily the weapon itself… But there are cases for everything, as far as the Ar-15 design is concerned: cook-off rounds making the receivers explode, barrels overcooking, gas tubes melting, bolts breaking, etc…

        The AR-15 (direct gas impingement system) has much more problems than the AR-18 (gas-piston system) and that is an undisputed fact… More cleaning required, which can become quite cumbersome and impractical in the middle of a fight; the overheating of the barrel and the bolt can provoke all kinds of troub, from overheating gas tubes but also depending on how resistant the gas tubes are, whether a cook-off happens before the gas tube melting or vice-versa, th fact is that there are examples of both floating around Youtube and forums…

        Logziz’s rifle won’t have these problems though, being a long-stroke gas piston system, much less prone to jammings of this sort…


      • 276 pedersen

        This is just anecdotal so take it for what it’s worth. I’ve seen issued M16A2’s have cook-offs on military ranges. These are rifle lying on the ground, pointing down range going off by themselves. Which is why you should clear weapons 🙂

  • Bryan S.

    With a slight relocation to Austria, he could make it big and Glock could have that carbine everyone has been asking for.

    I think I might be up for one of these….

    • You and me both Bryan. I want this so much more than an RFB now. I love how it uses an existing lower receiver.

  • Rick

    but I won’t be able to use all my standard AR uppers with this, will I?

    • Bobby

      You can with the system I’m designing. 🙂

      • Rick


        • Bobby

          Thank you.

  • louie

    outstanding work.
    cant waite to see your second wepon.
    simple elagent sloution a fully ambi. gun

  • Nathan

    Very appealing design. I think the use of the AR lower is genius. Great Work!

  • JCM10X25

    Two detail changes. First lose the loop pistol grip. Duplicate and incorporate the mounting fixture on the rear corner of the AR-15 lower receiver to accommodate standard and aftermarket AR-15 pistol grips. This will enable rifle to be optimized for FEMALE users. Why forfeit half of your potential market? Women fill support and combat support roles throughout entire U.S. and allied militaries. To say nothing of sworn agency peace officers and any number of private sector and individual purchasers. Second, if barrel mount to receiver can be redesigned to allow quick change with correct headspace for all five calibers usable by Longziz #2 magazines, you will have created a new WORLD STANDARD shoulder weapon for the PLANETARY Special Operations Community.
    Food for thought.

  • Boomtown

    Very interested… please let us know when it comes to market, so we (I) can purchase..
    Very Fine job… very innovative design… will no doubt work well in field, “entry”, and/or military application… I for one will, will be in line to pick one up … please advise…

  • Neco777

    Anyone have the patent number for this?