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Thread: Gas Piston vs Direct Impingement AR-15 system

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    Default Gas Piston vs Direct Impingement AR-15 system

    In starting my research for my next rifle build I'm looking at this new type of system - the gas piston. So far it looks like the gas piston system is a cut above the standard AR15.

    When the rifle is fired, the developing gases expand inside of the gas block much like a traditional DI system. The expanding gases push against our short stroke piston which exerts pressure on the operating rod and thus gives momentum to the bolt carrier. Once the piston itself has traveled 3/4", it expels any unused gas from a small vent in the bottom of the piston tube. As the cycle of the action is already in progress, the piston moves to the back of its chamber awaiting the return of the operating rod to push it back into battery.

    Here are a couple of animations that show the differences. (you can toggle between the HK for the GP and the AR for the DI by clicking the button in the bottom right corner)

    http://www.armytimes.com/projects/fl...02_20_carbine/

    The primary benefit of going Gas Piston is a higher level of reliability by running a cleaner and cooler AR by moving the operation of the rifle from the upper receiver and bolt carrier to the front gas block using a small diameter short stroke piston which does not require constant cleaning or lubrication like a Standard DI (Direct Impingement) AR does in order to ensure functionality.

    Also, you can have your AR cleaned in 5 minutes, vs. 30 minutes with a normal AR.

    The Bolt Carrier and Charging handle are broken down the same way, and the Gas Piston Tube is located inside the Gas Block and is removed by pressing on the piston tube nut release button, turning the tube and removing it by pulling it out.

    Then the tube is broken down very easily by removing the cross pin, removing the nut and taking the piston out of the tube.

    As for recoil - with the Standard AR the action is direct blow back into the upper receiver and the recoil is felt more in the upper receiver, closer to your face and shoulder.

    The Gas Piston System uses a small diameter piston that only travels about 3/4" and meets the fixed op-rod (which is affixed directly to the Bolt Carrier Group). The Recoil is not as harsh since the action is now occuring in the gas block at the forward part of the rifle, plus the excess gas is blown out of the gas block.

    Does anyone have any experience with a gas piston system and what do you think?

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    Default Re: Gas Piston vs Direct Impingement AR-15 system

    BTW, I've found a couple of places that sell the gas piston systems. Bushmaster and Addax tactical.

    http://www.bushmaster.com/catalog_xm...A3F16M4-GP.asp

    http://www.adxtactical.com/store/pc/home.asp

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    Default Re: Gas Piston vs Direct Impingement AR-15 system

    Gas operated extraction and spring reloading systems go back in US ARMY weapons to the M1 rifle and the M1 Carbine. Blow back systems are less dependable. AIRBORNE! GERONIMO!!

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    Default Re: Gas Piston vs Direct Impingement AR-15 system

    I have zero experience with thm. However, I've had to moderate a number of heated discussions about them over on arfcom. It's amazing how upset people become when you either tout something as the next holy grail or challenge the old one.

    You'll find industry people claiming it's the best thing ever while other industry leaders telling you it's a fix for something that isn't broke. I have read accounts from distributors and trainers claiming ALL piston uppers have had functionality issues. On paper, they look superfantabulous. In the field, you experience malfunctions. Again, this isn't from my experience - only from reading the countless topic discussions on AR15.com.

    If I intended to build a new rifle, I'd probably go for a Sabre, Lauer or LMT lower and a LaRue or Noveske upper. Or, if I went the LaRue route, I may even put my name on the list for a LaRue lower. People who buy ML's uppers have priority for his lowers. Actually, I think he only sells lowers to people who've purchased uppers.

    But not to sidetrack... If I was sold on the idea of a piston upper, I would take heed of the reports and wait to see if the manufacturers further developed them to address those short comings.

    We DO know what already works well. If something does the job it's designed to do then I'd stick with it. A weapon with decades of combat proven effectiveness has its advantages.

    I think a lot of people were taken in by the "wow its new and cool" factor. They spent a lot of money on it and are now trying to defend / justify their investment.

    A (poor) fix to a non existant problem, from what I've read.

    Oh, and as far as cleaning, the membership is saying you'll have to clean that bugger just as much.

    Good luck with whatever you decide. No matter what your choice turns out to be, the important thing to remember is (as my friend Old_Painless says), "Shooting stuff is fun." And that's all that counts.

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    Default Re: Gas Piston vs Direct Impingement AR-15 system

    Good post LJ. It appears that the debate over the gas piston system vs the standard DI system is like Ford vs Chevy or the like. Personally, I would think the gas piston system would be given some credence due to the success of the H&K battle rifle that is regarded as one of the best battle rifles in the world. Opinion? As for me personally, I've built an M4gery already based on the DI platorm and I figured my next build would be of another flavor - but I definitely don't want to build something on a platform that parts won't be available for or that turns out to be sub par (like the VHS vs Beta or Blu-ray vs HDDVD).

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    Default Re: Gas Piston vs Direct Impingement AR-15 system

    People bring your point up often. The piston system works well for the H&K. No arguing that. But trying to adapt an already functioning system with something that works well on a completely different weapon will not guarantee mirrored results. Different platforms often require different internal functions. I believe it is that simple.

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    Default Re: Gas Piston vs Direct Impingement AR-15 system

    That is a good point LJ. Any idea how long the AR version of the GP system has been around? I know the Army was looking to develop this into the new M16 replacement rifle but ended up shitcanning it.

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    Default Re: Gas Piston vs Direct Impingement AR-15 system

    I do not know. :)


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    Default Re: Gas Piston vs Direct Impingement AR-15 system

    I want that HK 416 and 417, but I keep hearing they're either LEO only or just plain not available in the U.S.

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    Default Re: Gas Piston vs Direct Impingement AR-15 system

    I do not have experience with the "improved" system but I do have a big boner for it.

    I like the idea of a cleaner and cooler system. I do not think it is as valuable to us regular folks who are not putting 10-15 magazines at a time downrange at stinky in the sandbox. The benefit is under continuous fire and a lot of time between cleanings.

    If you are going to build a new AR I would recommend trying the improved gas system. IF I had the cash I would build and AR using the "new" system and a 6.8 or 6.5 round instead of the usual 5.56.

    Either way though I look forward to the gun porn.
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    Default Re: Gas Piston vs Direct Impingement AR-15 system

    Also take a look at the Patriot Ordinance P-308, which is now on my short list. (Uses Gas piston system)

    http://www.pof-usa.com/p308/p308.htm


    "Where is the prince who can afford so to cover his country with troops for its defense, so that ten thousand men descending from the clouds might not,in many places, do an infinite deal of mischief before a force could be brought together to repel them?" -Benjamin Franklin, 1784


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    Default Re: Gas Piston vs Direct Impingement AR-15 system


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    Default Re: Gas Piston vs Direct Impingement AR-15 system

    Lemme weigh in here....the H&K system is not available cept for govt contracts. I have not heard of any agencies except rumors of SOCOM having them.

    POF and LWR are so far behind in production the civilian market won't see them soon.

    The LWR rifle is awesome I have shot a full auto 11" and it ran like a raped ape. THe mag well never heats up, its clean, and I was impressed. Sadly it seems it will be like the H&K elusive and unavailable.
    trying to survive our caring politians


  14. #14
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    Default Re: Gas Piston vs Direct Impingement AR-15 system

    I'm no expert by any means, however I have shot my fair share of AR's I have the Gas Piston Bushmaster and I must say it is the shit, went to the range the other day and blasted 100's of rounds, very nice indeed.

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    Default Re: Gas Piston vs Direct Impingement AR-15 system

    What does it do that your other AR does not?


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