HAR’s prototype AR-15 piston system

A new company called Holland Automatic Rifles (HAR) are developing a new AR-15-style upper receiver and piston system.

John from HAR explained how their system works …

It works on a new principal, of venting most of the unused gasses before they enter the piston. Then actuates the piston, before venting at the mid cycle, then vents a third time as it returns to rest. All of the exhaust gasses are vectored, so as to reduce muzzle climb, and torque twist. This principal has proven to need little or no lubrication, and acts as a cooling aid as well.

I am sure John will answer any questions you may have.

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.


  • Mouse

    Huh, interesting… Are their any animations of it in operation?

  • Carl

    Questions… how about a picture or a schematic that shows us how it actually works?

    How does it help cooling?

    Venting gases before they do any work (other than in the first half of the barrel) seems wasteful to me.

  • KTB

    That’s… Actually a decent sounding principle to make a piston system around. I wonder if the design will use a different bolt and carrier than a standard piston system…

  • Tony

    Err… Unless I misunderstand something, you can hardly call a slight variation of the piston system seen in many firearms before a new principle?

  • Lance

    Another new M-4 for a upgrade compation.

  • Whatever

    Should it be ‘principle’ rather than ‘principal’?

    It’s hard to comment on a design when no specifics are given.

  • mmathers

    Kind of looks like the bolt assy of a Keltec SU16. I’m curious to hear how this may be any different.

  • LurpyGeek

    Also, I’m curious how far along this is. It sounds like it may have a small amount of promise, but all we have is a simple schematic and a low quality picture of a rough machined prototype.

  • Martin

    I’d say lubrication is the key word in using a piston system. One of the major faults of the AR series, in my opinion, is the amount of spent propellant that is blown back into the action.

  • Freiheit

    @Tony its a non-trivial improvement on an existing design and is patentable.

  • sd1023x

    MMMMM…interesting…no recoil buffer tube?

  • Nooky

    Where is the bolt spring located ?

  • Carl

    I don’t know if that’s the recoil spring around the piston on top. But the bolt carrier still looks like it is long enough to prevent a folding stock.

    The Para TTR has the spring on top and no buffer, so you can use a folding stock.

  • David

    Yes, no recoil buffer tube. Welcome to the world of gas piston systems. 😉 For mature piston products, look at Robinson’s XCR (www.robarm.com) or Bushmaster’s ACR (bushmaster.com).

  • El Duderino

    No need for a recoil buffer tube with a gas piston system — the spring is over the barrel, not in the buttstock.

    It does kind of look like the SU-16, but then a lot of gas piston designs do. I’m a little lost as to why all of this gas venting is going on, but it sounds almost like the gas block is acting as a recoil compensator.

  • gyrfalcon

    What separates this from other piston systems for the M-16/AR-15 platform? LWRC, Bushmaster, H&K, Ruger all have piston products, some of which are already fielded by the US military.

  • dmurray

    The piston fad will last three more years, then “retro” direct gas impingement will come back into fashion.

  • John

    The return spring is telescoped outward from the rear of the buffer asembly/impindgement key.
    It is not an su16 bolt assy, although the front half of the m16 bolt carrier is used.
    Cooling is aided by triple venting, which acts as an air pump on the return cycle.

  • John

    Notice aft of the upper. The return spring assy keeper is visible, which is also the receiver end plate. The receiver is proprietary, as is the rest of the parts in the white. The barrel is Lilja, which is what we will use for the first production run.

  • John

    We do not currently have the animated version, as the program is not in our budget.
    The first prototype has been tested with 12,000 rnds, and has exceeded our expectations and all other manufacture’s claims. This version is in production at our aerospace engineering and machine facility. It goes to market late summer.
    The folding stock version will go into the testing phase soon. We hope to bring it to market, spring 2011.
    The third version, (a free floating forend with captured piston system)for D.M.R use.

  • John

    The model, and the photo are not the same. The model is the S I Q R 1. The photo is the S I Q R 2

  • C3P0

    So, it shoots crayons?

    (yeah, I know, the guys probably put their effort into designing and improving and not modeling bullet shapes, but if it does shoot crayons, We should all be buying Crayola stock)

  • Vitor

    Hey John,

    All this ventig reduces recoil in any considerable measure?

  • sd1023x

    “David on 20 May 2010 at 1:32 am link comment

    Yes, no recoil buffer tube. Welcome to the world of gas piston systems. 😉 For mature piston products, look at Robinson’s XCR (www.robarm.com) or Bushmaster’s ACR (bushmaster.com).”

    Too bad XCR is a piece of junk.

  • John

    Excellent question, The venting of the dirtiest, hottest gasses. Has a considerable affect on muzzle rise, recoil, and torque twist. So much so, that a 50 rnd burst has a 7.5″ spread @ 50 meters.

  • John

    I am familar with those products, but have not had the opertunity to fire them. The xcr seems to be a good version of a stoner type system. I believe the acr is a mag pull design, and appears to be quite well thought out.

  • John

    El Duderino
    If there is a return/recoil spring above, or below the barrel for that matter. It is a long stroke piston, usually connected to the bolt or carrier. This has an adverse affect, due to high recriprocating mass.

  • Ken

    Hows spring life considering its over the barrel? Will standard bolts fit your rifle? Will this possibly be sold as a retrofit kit for other AR rifles or will it be sold as a whole rifle? Any water collection in the piston system after a “bath”? Just curious btw. Who did the testing of “50 rounds at 50 meters”? Musta had ammo to burn because really who will shoot it like that? Must have been a scientific test 🙂 -ken

  • John

    The spring on both models shown that is captured by the op rod, is strictly for the return of the piston, link, and op rod.
    Standard bolts will fit, but must be notched to accept charging handle lug. The system can be sold as a kit, if you already have a side charging upper. The piston system will not work with the standard upper, because the carrier key occupies the space where the charger was. Water does not stand in the piston, as long as the bbl is not pluged. Our testing was done at various times, and locations. They were conducted by Mp, Leos, and vets under controlled sircumstances. The model one has had 12,000 rnds put through it, so we have burnt lots of ammo. It will even digest the worst steel cased russo crap, with out a hiccup!

  • John

    The para ttr, and the zm line are not short stroke pistons. The zm is not even a piston rifle, it is DI. I also do not believe that they will run full auto, as there is no provision for that sear on a shortend bolt. The HAR SIQR 2, does however have a proprietary trip lever allowing for select fire.

  • gyrfalcon

    “The piston fad will last three more years, then “retro” direct gas impingement will come back into fashion.” — dmurray

    I’m fine with direct gas impingement as long as the exhaust doesn’t go back into the mag/boltface/chamber area… Maybe Eugene Stoner didn’t go camping much and never realized you shouldn’t go to the bathroom in the same location you pitch your tent.

  • John

    Well said. The m16/ar15 ia in my opinion, the finest combat rifle to date. That being said. The di op system is also not in keeping with combat hygene, to say the least. That does noy detract on the fact that stoner was exceptonial.

  • Tan

    That design kind of reminds me of the AR-180. My complaint with pistons (long or short stroke) is it changes the recoil axis of the gun. Direct Impingment is still a piston, carrier pushes itself back against the bolt, on the same axis as the bore. Once the carrier is in motion, inertia takes over and pulls the bolt out of battery. Take the gas rings off and it ceases to function, see? piston, just not the traditional arrangement.

    Maybe not the best design for a combat rifle due to hygeine problems, but definitely a better smoother shooter from a purely mechanical standpoint.

    Putting the piston over top of the bore can only add to muzzle rise which also explains why the M1 and M14 put their gas systems below the barrel so it pitches down against recoil. Otherwise things need to be tuned more carefully or very low mass to prevent pitching the gun up.

    Dual port pistons like this one might have problems with different ammo if it isn’t developed right but to me this design seems like prior art, maybe not on guns but its basically a spool valve or logic valve already in use. Still without a guide system the carrier is going to tilt, standard AR upper just isn’t made for it.

    There are already close to a dozen pistons on the market with comments of ours is better than the other guy’s but unless the military buys one it won’t be supported or standardized in the long run, just look at what happened to the AR-10 before its adoption. I’ll stick to the DI standard and lots of oil to keep crud off, chrome helps a lot.

  • shockfish08

    So… I can’t find a website or a link to anything else about Holland Automatic Rifles. Where did you find this information? I’d like to know more about the design.