Dual Gas Piston / DGI Patent

Jason Jackson has received a patent (#8,176,837) for a AR-15 gas system that can be switched from piston-mode to direct impingement-mode by the operator. The piston itself is the gas tube. By adjusting the system, the piston can be locked in place and opened up to allow gas to flow through it into the bolt carrier.

I have racked by brain trying to think of a situation where a dual systems would be preferable over a just gas or just piston, but I can’t. It seems like needless complexity to me.

[ Many thanks to John for emailing us 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.


  • I think so people forget to ask why before they do something. I can’t image an situation where i’d want to switch from one to the other.

    • spc fish

      the only time it could ever come in use is if a preson who loves DGI guns wnts to put a suppressor on and swith to the piston to keep gas out of their face. but thats rare. usually people jsut put up with it or go all piston

    • spc fish

      the only time it could ever come in use is if a preson who loves DGI guns wnts to put a suppressor on and swith to the piston to keep gas out of their face. but thats rare. usually people just put up with it or go all piston

  • Reverend Clint

    its another solution to a problem that doesnt exist… like 2 barrel ar’s and 1911’s

    • Joe Schmoe

      Well the dual barrel AR might have a point if it can pen. body armor.

      This though has no discernible feature other than “it can be done”.

      • matt

        “Well the dual barrel AR might have a point if it can pen. body armor.”

        You’re an idiot, we went over why that will never work in the previous thread.

      • Joe Schmoe

        Awww… resorting to insults are we?

        So tell me, you have evidence that two 5.56mm rounds landing less than <3 inches of each other nearly simultaneously will not penetrate body armor? Please do post or shut up.

      • shiddymunkie

        @Joe Schmoe

        The burden of proof is on the person making the assertion. If you’re asserting that a dual-barreled AR will increase body armor penetration over a single-barreled AR, then the burden of proof falls on your shoulders.

        You can’t simply assume something is true for no other reason than because it has not been disproved yet. There should be evidence supporting the initial belief *before* that idea makes it to peer review.

        With that being said, what evidence led you to believing that a dual-barreled AR will penetrate better in the first place (before you began relying on other people to “prove you wrong”)?

  • Mike

    I guess.. maybe.. if your rifle catastrophically failed except for the BCG, and you found a rifle that had a different set-up… :scratches head:… Maybe for blanks, or barrel mounted grenade launchers? I don’t know.

  • Weezy

    We already have both piston and DI systems that can have their gas systems adjusted and I don’t recall people complaining. Why should this be any different? Don’t want it, need it, or think necessary? Fine, don’t buy it. But it doesn’t mean people shouldn’t keep innovating and coming up with new ideas or improving “old” ideas in the firearms world.

  • pisssssssssssssssssss

  • Lex

    Innovation for the sake of innovation is something I can respect even if it doesn’t produce anything immediately useful.

    • Gidge

      Innovation for the sake of innovation may not directly produce anything useful, but it’ll often become a technological stepping stone or provide inspiration for something that is useful.

      Modern refrigerators wouldn’t have been possible without some “useless discoveries” from chemical weapons research

  • Denderwuz

    Run it as a piston to prevent fouling…. if a part breaks it fails safe as a DI rig… I like it.

  • RedRalph!

    Because it will sell in the civilian market. And people will find their own reasons of why it will be useful.

  • Laingatang

    Run it as a DI system for accuracy and switch to piston when the weapon is suppressed? That is what I imagine it would be useful for.

    • Lex

      I thought piston systems didn’t do particularly well with suppressors.

      • Laingatang

        Suppressors cause more gas to be bled off the barrel which in DI AR-15s means a lot more gas pressure coming out the ejection port than normal and potentially into the users face. Using a piston conversion causes the gas pressure to be dissipated in the gas chamber. In my experience each operating method is just as reliable as the other operating while suppressed.

  • -V-

    Run it as DI for accuracy and switch it to piston for reliability/minimize fouling for FA/Rapid fire, or aforementioned piston for suppressor use, DI for regular use. I like it, plus it doesn’t really add any complexity over a standard piston setup either.

  • Gidge

    Run as DGI for normal use. Switch to piston for suppressor or if you’re having problems cycling.

    Also if you normally use DGI but want to fire un-jacketed rounds for some reason you can switch to piston

  • Overthetop

    Not all patented designs are meant for the market as an actual product. Maybe it’s use is more to keep competitors out of the IP space the inventor is working in?

  • Zach

    This really needs to incorporate a recoil operation system and roller-delayed blowback system as well. Then it would be uber-cool and worthy of my super secret special operator ninja missions.

  • Logan

    Why not?! If he wants to do something just because he can why the hell not? I agree it may not do anything but maybe he’ll stumble onto some revolutionary idea that changes the whole AR world.

  • Big Daddy

    Science, innovation, design and building just for the sake of it, answering the question can it be done rather than why. That’s what makes the world great and it fuels the forward movement of civilization.

    You don’t need a reason other than you can. Most inventions were made that way. Very few inventors other than Edison actually thought about if they can make money, some did, most did not, such as Tesla. Benjamin Franklin never patented some inventions we use today, he thought it benefited mankind and he was happy with that.

    We need more people trying to invent things. We need more people trying to solve problems. For all we know someone who reads that patent sees it as a way to solve a mechanical problem concerning something totally NOT related to firearms. That’s the way science works…….

    • dylan b

      colt canada did infact make a hybrid prototype that never made it past that stage. i seen it first hand when i was working for a general dynamics manufacturing contracter some months back (colt canada and general dynamics work very closely in canada). long story short it was what they called a flow through piston. the main piston rod had a hole through the center. when gas would flow through the piston assembly the theory was that 50% of the operating force would be made up by the piston and 50% would be created via direct impingement. it was supposed to run cleaner and have much less punch then other piston guns but as it turns out the piston did absolutely nothing and the gun was just running soley on di. it also came in 6 oz heavier then the current “iur carbine” and something like a full pound heavier then the current c8a2. in the end its definately a good idea that needs more work

      • dylan b

        sorry meant to tag this to comment by W

  • W

    doesn’t Colt already have a hybrid DI/gas piston system?

  • Lance

    I like it get the best of both AR worlds in one rifle.

  • Tinkerer

    I commend the creator of this design for thinking outside the box, and proposing something new. My respect goes to them.

    The problem I have is with the “piston-driven rifles are less accurate than DI-driven rifles” rationale, when the long-stroke-piston driven SIG 550 is subject to -and accomplishes- a higher accuracy standard than the most ubiquitous DI-driven rifle -the AR-15 family-. So, a piston rifle CAN BE just as accurate as a DI rifle, there is no inherent lack of accuracy due to the operating system itself. The most belittled piston-driven rifle -accuracy-wise, of course-, the AK, has more to owe to it’s sights, caliber, QC and loose tolerances than to it’s piston when it comes to long range accuracy.

    • Laingatang

      Oh, I didn’t realise the SIG 550 was so accurate, unfortunately I have never been fortunate enough to hangle one. Most of my assault rifle experience is with AUSTEYR F88s, AR-15s, AK-47s and SLRs (FN FAL). And the AR-15 has proven itself to be the most accurate semi auto I have handled. A SIG 550 is now on my bucket list to try out though!

    • FormerSFMedic

      Those that say that a piston gun (in general) is not as accurate as a DI gun would be wrong for sure. However, in the AR platform, this theory is true. It has been proven. Most honest AR manufacturers will even tell you that their DI guns are more accurate than their piston guns. Unfortunately is just a part of physics we can’t get around.

  • Trev

    Cool, more parts to break.

    • Laingatang

      I wouldn’t think that this would have any more parts than an adjustable gas piston does.

    • Cymond

      And if the additional parts DO break, the gun should continue to operate in DI mode.

  • mosinman

    ¨I have racked by brain trying to think of a situation where a dual systems would be preferable over a just gas or just piston, but I can’t. It seems like needless complexity to me¨…… yeah but its pretty damn cool though!

  • Stanislao

    This is what happens when engineers lack discipline. We start to think what can we do instead of what should we do. Unfortunately, no-one really teaches this.

  • aaron y.

    theonly possible earthly idea i could place would be in a full auto gun to alter cycle rates, however this isn’t truly praticle and loks like a worthless peice of crap to me.

  • Nanban Jim

    This is actually a pretty good patent. Charybdis seems to be a small (1-man?) company. By getting a patent approved, Jason proves that he is capable of producing (or managing those who produce) novel ideas. Novelty/unexpectedness is a core requirement of a patent. Even if this were 100% provably stupid, the fact that it’s NOVEL is important.

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  • Sam Suggs

    WHY? is the only question that needs an answer hear however if he can sell it power to him