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Thread: Piston or Gas?

  1. #101
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    Several advantages go with the gas piston design. Whether or not they are appreciated by ALL of the buying public is moot.

    [1] The chamber temperatures will be lower which will improve or enhance the life of the springs in the bolt head.

    [2] A cleaner chamber also makes for a statistically improved reliability. How much? I have no idea as each shooting event will vary and cannot be controlled.

    Are there any disadvantages? In theory, yes, same with the advantages listed above. Will they occur with a frequency to make them significant? Time will tell.

    [1] More parts equal a greater chance for failure. But when we see a bolt carrier sans carrier key, two screws, loctite and staking and no gas rings ( 8 parts including staking exercise ) I don't think we have an increase in parts at all. BUT THE PARTS ARE DIFFERENT AS WILL BE THE FAILURE MODES.

    [2] There is a slight increase in felt recoil - okay, not a reliability/durability issue but is something that is unique to the design and even though it's slight, it's noticeable and not for the better, ultimately.

    [3] Proprietary parts. That, to me, is the potential killer as is the next disadvantage

    [4] Carrier Tilt (ouch!)

    [5] Price.



    I, too, am a degreed engineer with a BSME in Thermal Science and 14 yrs experience in Vibrations and Acoustics and 7 yrs experience in high temp and wear resistant coatings. The Gas Piston CONCEPT is *THE* way to go, period. Whether or not any of the current AR-15 adaptations represent decent execution of same remains to be seen.

    P.S.

    If anyone wishes to "unload" their ill-performing (even in their mind's eye, only) DGI or GP AR-15s just drop me a line. Since they are "flawed" I'll require a hefty discount.

  2. #102
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    Quote Originally Posted by Mjolnir View Post
    Several advantages go with the gas piston design. Whether or not they are appreciated by ALL of the buying public is moot.

    [1] The chamber temperatures will be lower which will improve or enhance the life of the springs in the bolt head.
    Have you seen data from a DI gun versus a piston -- chamber temp is 99% from the fired casing. You will see a warmer bolt from the Di gun, as the piston in the DI gun is the Bolt head - and hot gas does affect it directly.

    However I think you will find the unlocking of the Piston gun much more violent.

    Depending upon the quality of the spring being used the spring (ejector or extractor) can take a great deal of heat, and lose very little strength and cooling/heating while being cycled does in fact take a very little from ther spring life.

    [2] A cleaner chamber also makes for a statistically improved reliability. How much? I have no idea as each shooting event will vary and cannot be controlled.
    Chamber fouling is not specific to DI - its related to the unlocking time, and pressure in the barrel.

    Two of you basic premises are flawed in relationship to Direct Inpingment.


    I'm not an engineer, but I've got 24+ years of working with the M16FOW, have shot over 1,000,000 rds and seen several countless million through them, plus have a bunch of Engineers at work, and a lot of differnet test on springs and the actions of weapons.
    Kevin S. Boland
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    FN America, LLC
    Office: 703.288.3500 x181 | Mobile: 407-451-4544 | Fax: 703.288.4505
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  3. #103
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    It's been awhile since I've been on here, and I honestly haven't been keeping up with the whole 'piston debate'.

    That being said I'm inclined to accept what Dinger's says, namely that the 416 is the only way to go...IF you want a piston.

    How does the HK system deal with carrier lift?
    "So have your buddy get a box of stray cats and try to get a good sight picture while he is throwing the cats at you... naked." - KLD

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  4. #104
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    Quote Originally Posted by Mjolnir View Post
    Several advantages go with the gas piston design. Whether or not they are appreciated by ALL of the buying public is moot.

    [1] The chamber temperatures will be lower which will improve or enhance the life of the springs in the bolt head.

    [2] A cleaner chamber also makes for a statistically improved reliability. How much? I have no idea as each shooting event will vary and cannot be controlled.

    WHAT!? How does a having a piston affect how clean the chamber is? The gas from the gas tube acts on the back of the bolt and inside the carrier and doesnt make its way into the chamber hence why we replace the gas rings to ensure a gas seal. Having an engineering degree doesnt make you an automatic expert in firearms operating systems. I think you should read up more on the AR-15s operation.

    I would suggest this:
    http://www.ar15barrels.com/prod/operation.shtml
    Last edited by vicious_cb; 09-14-09 at 06:40.

  5. #105
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    Quote Originally Posted by JLM View Post
    It's been awhile since I've been on here, and I honestly haven't been keeping up with the whole 'piston debate'.

    That being said I'm inclined to accept what Dinger's says, namely that the 416 is the only way to go...IF you want a piston.

    How does the HK system deal with carrier lift?
    Even HK's have problems with carrier tilt. However their bolt is designed to minize the effects of this.
    Kevin S. Boland
    Manager, Federal Sales
    FN America, LLC
    Office: 703.288.3500 x181 | Mobile: 407-451-4544 | Fax: 703.288.4505
    www.fnhusa.com

  6. #106
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    Quote Originally Posted by KevinB View Post
    Even HK's have problems with carrier tilt. However their bolt is designed to minize the effects of this.
    can you be more specific?

  7. #107
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    I have a uncle that worked for the FBI as a weapons examiner and later a armorer and a good friend who both (uncle and friend) have worked with and around the dea. And as I can remember when the p90 was getting hyped up they bought a pretty pennys worth before they figured out how ballistically sucky they were. Just sayin, doesn't seem that the dea has a good track record for doing there homework. I'm not saying the lwrc or any piston ar is bad or good. Just that basing a judgement on the dea's is not a real good idea.
    "Calling an illegal alien an undocumented immigrant is like calling a drug dealer an unlicensed pharmacist"

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  8. #108
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    Obviously they learn from their mistakes. They went straight to the top with LWRC.

  9. #109
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    Quote Originally Posted by dmanflynn View Post
    I have a uncle that worked for the FBI as a weapons examiner and later a armorer and a good friend who both (uncle and friend) have worked with and around the dea. And as I can remember when the p90 was getting hyped up they bought a pretty pennys worth before they figured out how ballistically sucky they were. Just sayin, doesn't seem that the dea has a good track record for doing there homework. I'm not saying the lwrc or any piston ar is bad or good. Just that basing a judgement on the dea's is not a real good idea.
    This is true for ANY agency. When I was selling guns we sold a ton of USPs simply because the local PD changed over to them.

  10. #110
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    As the armorer for my department, I have been the guinea pig, having been issued the only piston AR. I have been to several instructor schools with it and have used it non-stop in training and teaching. Well over 7K rounds through it.

    Do I think it is the end-all system? No. I still have reservations about it though it has never failed me. I can say I like it so far.

    Due to the nature of the beast, I would NOT recommend it to a neophyte. As previous posters have noted, learn the DI system first before getting involved in GP, unless of course you are familiar with a system like the FN FAL, which most piston systems seem to copy.

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