12 Gauge AR-15 Upper machine gun!

This is awesome:

Derek writes:

I have designed and patents pending on this.. Its a beltfed 12 gauge upper receiver for a ar-15 or m16 lower receiver. It uses your lower receiver, so if you have a ar15 its a semi auto shotgun, however if you have a registered m16 lower or a drop in auto sear it becomes a full auto 12 gauge machine gun. This is a prototype model and all the bugs arent worked out quite yet. Most of the problems that I have encountered revolve around the shotgun sheels not being consistent enough to eject sometimes.

I will be doing a brief interview with the Derek soon.

Hat Tip: Say Uncle

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.


  • 1 vote for coolest AR upper ever.

  • *D.R.O.O.L.*

  • Don

    So impractical, yet so cool… I want one badly…

  • jdun1911

    Too much stoppage for my liking. Keep work on it tho.

  • That’s pretty slick! Although I agree, it jams up way too often. Any idea on weight?

  • Blake

    That is sweet, I want one. I would prefer a horizontal magazine instead of a belt with ths design but still awesome.

  • Eddy Alvarez

    is this guy shooting in his back yard? i’m so jealous.

  • This looks like an ideal home defence weapon- if you’re facing off against zombie hordes that is.

    Very cool.

  • luv2ski

    Cool. Has ATF tech branch classified it as a non-gun, non-DD? They are following a bizzare path these days with AR uppers that have magazines and feeding mechanisms. Just look at what they did to the XMG AR upper:


  • Reid

    Very cool indeed. Though I don’t expect to ever own something approaching this in California. Even the belt (if 10+rounds) is illegal here! Not to mention it’s both a SBS and a machine gun.

  • David Johnston

    when da bugs is worked out i will be giving you a call. the deer in michigan just wont have a chance.

  • I agree with the mag fed upper.

  • Tomasco

    Watching that just made me grin really big…. When I was in the Navy our skipper let us shoot the twin 40mm on the stern of our ship. This reminded me of that in a way.

  • J.A. James

    In reverse order of priority:

    1. A full auto, belt fed 12 gauge shotgun.
    2. A place to live where I can fire said shotgun from the window of my garage and not go to jail.

    On a more realistic note, the designer should get in touch with CZ in Brno, Czech Republic. They’ve got rights to patents and designs for most of the old Czech Design Bureau’s firearms designs.

    In the late 50s, early 60s, they experimented with a belt feed conversion for surplus Bren light machineguns. (Which itself was essentially a design ripoff of an earlier Czech design). Anyway, the Czechs were almost ridiculously meticulous in their testing and documentation. They’ve got figures for belt tension, round spacing, degrees of curve in the belt, pretty much anything you can think of.

    The beast in the article looks to be fairly serviceable until the curve in the belt gets too severe. In Vietnam, this was a problem with some helo mounted M60s which were resolved by soldering a C-Ration can to the receiver. Looks to me like the shotgun here is having similar issues caused by the weight of the rounds and the degree of curve in the belt. A pretty simple redesign of the feed tray should clear up the big problem shown in the video.
    Also, think seriously about feeding directly from an ammo can mounted to the feed tray. That solves most of the problems with the belt dropping off your window frame and stopping your gun.

    As always, YMMV

    • J.A., did the CZ conversion fire 12 gauge?

    • Rick Randall

      Um, the Bren gun WAS NOT a “rip off” of an earlier Czech design. It WAS a Czech design, modified from their 7.92mm LMG lines for the British .303, and licensed to the British government (which was ALWAYS a part of the RFP).

  • J.A. James

    Hey Steve,

    I’m still hating life when it comes to files and documentation. Still unpacking after a major move and I had my friends help. They helped by packing everything in whatever space it would fit. Things like file folders and all of my external hard drives… sigh…

    As I remember it, the belt feed conversion of the Brens was an attempt to convert from .303 British to 7X54 Russian Long. I honestly can’t remember the name of the designer though later on he was one of the guys who got the Cz75 from design into manufacture.

    The Bren was always touchy even feeding from the magazine because of the rimmed cartridge. Gunners had to be very careful when loading the magazines to make sure each cartridge was loaded with it’s rim either directly on top or nested in front of the rim on the cartridge below. No stripper clips for those guys.

    Things just got too complex with the system when converted to belt feed and then remachined to take the longer, wider Soviet cartridge.

    I’m not sure the Czech info would be generic enough to help with the 12ga system in the article but the problems with wide rimmed cases in belt feed systems are literally as old as the machinegun itself.

    The only reason I brought it up was because I had a chance to talk with some of the Czechs on the ‘Soviet Military Liaison Mission’ teams assigned to the US 7th Army area in West Germany. For the most part the SMLM guys were pretty civil even to their avowed enemies in the US forces. I suspect I remember the Czechs better because they struck me as pretty decent guys in general and their level of technical expertise was easily on par with their US and NATO counterparts. The few other guys I met from the Soviet mission struck me as pretty generic military staff wonk types who’d lucked into a pretty cushy position working the western side of the Wall.

    Since then I’ve met and corresponded with other folks from the Czech Republic and their military historians are; at least in my view; among the best in the world. Meticulous documentation and extensive reference and cross reference. If my memory hasn’t gone completely south, most of the technical documents from the post-WWII era were stored in Brno and since given to the museum run by CZ on behalf of the Czech Republic government.

    Once I can find my old notes and docs, I’ll post the most current contact info I’ve got for them here. Just from a technical history perspective, some of the stuff the Czechs did is still mind blowingly fascinating. An awful lot of the ‘modern’ firearms designs are descended either from first generation Czech systems or earlier systems the Czechs worked with for the Warsaw Pact and then their own national arms industries.

  • Johann Van De Leeuw

    Man, I’d like one of those. (LOL)!

  • Hedonistic

    Will there be a 1 round belt for trap?

  • bullitt396

    Some type of a feed ramp secured to the upper might solve the feed issues. You’ve probably already opened up the ejection port a bunch to handle the differences between 12 ga lengths. I want one now when you solve all the issues. I want one now even with issues!

  • Thanks again for the article.Really looking forward to read more. Keep writing.

  • Sam Suggs

    now thats a metal storm

  • zernypersson@hotmail.com
  • mady

    wow i want one…

  • Zeus Smith

    and duck hunting will never be the same

  • Shotty

    Might have some feed problems

  • Bo Treat

    this would shred a human to tiny bits, scary thought of it ever being used for combat or anything else.

    • dfg

      idk, i mean it would yet… but with give distance of realistic round travel and other factors it would make it much harder, though this particular style/type is not bad, it is very much a novelty in the sense that we have auto shotguns in much better design that serve their purpose and a belt fed shotgun just has no practical military application… though i would still sure as hell own one…!