Fully Automatic .22 Cal Air Gun GMG (Gas Machine Gun)

Since I last wrote about it last year, the GMG (Gas Machine Gun) has come a long way. It no longer resembles a pistol carbine, but instead a large bullpup rifle.

The 50-round drum magazine is loaded with reusable shell casings. The gun can fire anything that fits into these shell casing. At the muzzle, it will push a 16gr lead ball at a speed of 600 fps (12.8 ft/lbs).

The receiver is made from steel. It has a 24 inch barrel and quad picatinny rails. Unloaded is weighs 7 lbs. It requires an external paintball-compatible tank filled with Nitrogen or HPA. The inventors are selling each of the 15 prototypes for $1,000. Not cheap!

The idea of practical air guns for self-defense and offense go back a long time. The most famous military-style air gun was the Girandoni rifle as used by Lewis and Clark. One notable advocate of air guns for self-defense was the late activist/inventor Philip Luty. Luty designed and published the blueprints for an air submachine gun although I have never seen evidence that anyone ever successfully built it.

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 fun wait till Liberals try to ban them.

    • Lance, I’m trying really hard to figure out if you’re intentionally trolling or you really are that misinformed.

      Why bash Liberals and Obama day in and day out? That drumbeat gets old fast, and makes you look much less an informed person and more a rabid pundit with no real knowledge.

    • Lance

      I was joking

      • JonMac

        In this case though, you would have had a point. This is already illegal in the UK.

      • jdun1911

        You shouldn’t apologized. Your statement is correct. Liberals will try to ban anything that they think is not correct. Only the liberal elites can have them and no one else.

      • Komrad

        I am a pro-gun liberal and I don’t believe in banning much at all, firearms related or otherwise. About the only thing I do think should be banned are things that are inherently dangerous to consumers (ie, lead paint baby toys, contaminated food, appliances that electrocute users) or things that violate the constitution (ie, religion in schools, vigilantism). I don’t think any class of individual should have access to anything that others don’t.

        Your generalizations are incorrect and are exactly the kind of thing that unfortunately turns people away from the shooting sports. People don’t want to hear about how liberals are trying to take their guns when they are a gun owning liberal themselves.

    • Komrad

      Not funny Lance, at least not to me. Liberal jokes get old fast, especially when they are patently false generalizations.

  • DaveR

    Hmmmmmm…yes, I would consider dropping a grand on this, even if the company might go away. As long as the construction is solid and the internals are easily maintained/serviced it could provide decades of fun! The only thing that gives me pause are the shell casings–run out of those and the gun becomes inoperable.

  • K!P

    hum dont like the shell casings..they seem to coplicate the thing witout really having a function besides looks

    • schadavi

      The function is the ability to stack pellets like in a firearm magazine.
      Without the shells, pellets and lead balls would be damaged by spring tension.
      This is pretty much necessary to build an automatic air-rifle.

      I personally thought of this before, and wondered why no manufacturer does this.

      • GeoffH

        I’m sure you could come up with some other method for feeding the ammo that didn’t require the casings, but it would likely be more cumbersome and expensive. The casings are a reasonably inexpensive solution to using this type of feed mechanism.

      • K!P

        there are more ways than the firearm way of using add on shells, many airsoft or paintball markers manage to load from magazines or hoppers witout add on casings. So do many semi auto air rifles. often using a tube magazine alowing a string of pellets or balls to be loaded into place witout damaging one.

      • Komrad

        those use paintballs, which are soft and flexible, or hard steel balls
        paintballs bounce back when deformed slightly and BBs are hard enough to not deform

        soft lead pellets would deform in a traditional magazine
        sure, you could use a revolver type rotating disc or a row of “chambers”, but those are essentially the same thing but without the ability to link them together for a larger ammo capacity

  • dg13

    Shell casings are a necessity.

    no way you could reliably feed 50 rounds of soft lead pellets without something like that. Most airguns use a revolver-cylinder like device as the magazine, to keep the pellets from touching each other…..other than a belt, not sure how else it could be done for an automatic airgun. Airgun Pellets were not really designed for use in magazines.

    Just add a small bag to catch all the casings when you shoot.

    • Komrad

      What about hard lead balls such as the ones that are used (well, supposed to be used) in the Drozd Bumblebee and the old Makarov airguns?

      It shouldn’t be too hard to make .22 caliber lead balls for use in these types of things.

  • anthony

    pa looty did not design the air gun only coppyed thedesign of the casselman airgun , a video of it in action is posted at youtube.

  • abprosper

    There was a BB (.177 like used in a Daisy air rifle) machine gun during the 80’s. I was too young and couldn’t afford one and by the time I had surplus cash and as old enough , the freon tanks they used to make them run were gone.

    The were fairly potent and while generally unsuitable as a defense arm, IIRC Massad Ayoob related a story of a woman used one to “hose down”” an attacker in her home and basically hospitalized him at that point

    • DaveR

      Wow! I actually OWNED one of those! I’m old. 🙁

      It was a POS and a **mess** to use. You had to coat all the BBs w/ graphite powder first, and then the cans of freon were good for about 5 seconds before they iced up and bacame useless.

      • abprosper

        I never knew that. Glad I never bought one.

        Thanks for the post

  • Arrkhal

    “The idea of practical air guns for self-defense and offense go back a long time.”

    I hope no one’s seriously considering this thing for self defense. The Giradoni was a .46 cal, you’ll notice. Something more like a modernized version of that would be a lot better for shooting anything larger than zombie bunnies. Quackenbush’s airguns are in about the range of .38 SPL power, IIRC, but in .458 and .50 cal.

  • Chrontius

    I want the old model. Are they selling *those* prototypes?

    • me

      There used to be a co2 airgun fully auto 9mm. Search its under bigbore airgun shoot

  • noob

    What’s the law on how much energy the pellet can have before it becomes a restricted weapon?

    I’m thinking that aftermarket parts to overgas the system shouldn’t be too hard to machine.

    Also, do steel bbs mess up the rifling?

    • Leo Atrox

      Check your state laws. They are unregulated at the federal level.

      I think my state is 1200fps before it is considered (by the state) to be a firearm.

      • Leo Atrox

        Ha! See, this is why you need to check. Apparently, my state considers anything with a muzzle velocity over 700fps a firearm. More specifically, “any pneumatic gun, spring gun, paint ball gun or B‑B gun which either expels a single globular projectile not exceeding .18 inch in diameter and which has a maximum muzzle velocity of less than 700 feet per second or breakable paint balls containing washable marking colors.”

        Gotta love Illinois. And by love, I really mean loathe.

        So, even if it doesn’t exceed 700fps, if its fires non-blobular projectiles, or projectiles exceeding .18 inch in diameter, Illinois considers it a firearm, meaning a buyer must have a FOID card and transport/care for it as if it were a real firearm. *sigh* If my wife wasn’t from the stupid state …

    • Zermoid

      The Gestapo State of NJ requires a FOID for anything that fires a projectile from a barrel, even a Daisy Red Rider BB gun!

      Pennsylvania does not regulate anything that uses air or CO2 as propellent. If it doesn’t use an explosion to propel a projectile they don’t care.

      • Duke Aquaro

        This is too funny. I actually bought a Red Ryder IN New Jersey with my Fireams ID card. I now live in Florida, thank you Lord. If you love to shoot, this is a great place to live. I still have that Red Ryder!

      • me

        Ya i read there was a law that was suposed to kkeep them from doning that

    • Komrad

      They can sometimes. the Drozd Bumblebee was sold with .177 cal steel BBs but was actually only supposed to be used with .177 cal lead balls to preserve the rifling. Shooting a lot of steel through them would ruin the rifling eventually. However, there is at least one aftermarket barrel available made with harder steel that is less susceptible. It all depends on how hard heir steel is and how the rifling is. I would suspect that a tighter bore would wear faster with steel than a wider one, but I have nothing to base that on other than hunches.

  • John Doe

    Oh air guns, I remember when my cousin came over when I was 14, and I showed him how to use it. Coming from inner Manhattan, he thought guns were stupid. So we were doing some target shooting, when he disregarded gun safety and shot me in the arm. It wasn’t that high velocity, and it was from a distance, but I still remember going to the bathroom, tying a tourniquet around my arm to staunch the bleeding, and pulling out the pellet with tweezers.

    Lesson of the story, these things are dangerous, is it regulated? I think after 11 years, I have a plan for revenge.

  • Bryan S.

    Well, you could also buy an SMG22, from http://air-ordnance.com

    Plus 25 belts and a 100 rd speed loader for the same price.

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