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Thread: Piston v. DI temp measurements

  1. #11
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    Quote Originally Posted by markm View Post
    I really hate when the Pistards demo that. They'll pop a bolt out of a recently fired piston gun and hold it in their hand AS IF you couldn't do the exact same thing with a DI gun.
    I think it's the CARRIER they mean but without endurance test data, impirical models and data what does it TRULY mean? We have to call this anecdotal. Yes, heat is not good when you add cyclical loading but just HOW much makes a difference? I dunno and to be honest since I don't know I cannot say I "care".

    The piston adds a little complexity and reduces "stress" by reducing temps on some critical items. It simplifies cleaning the bolt/bolt carrier assembly but the impact of the piston *may* reduce the bolt lug life - gotta see the correlated FMEA models and impirical data to know for sure. There is a weight (balance) penalty with the piston and the recoil impulse is sharper though the overall force hardly changes - it's still a 5.56 NATO cartridge.

    If you've got the coin and so motivated purchase the piston carbine. If not, stay with the D.I. carbine - google "Greg Pannone, AR-15 Reliability" and follow his advice if you stay with the D.I.

  2. #12
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    Quote Originally Posted by Mjolnir View Post
    I think it's the CARRIER they mean but....
    Either way.... I mean... I drop my bolt group out at the end of every shoot to get some CLP soaking into the carbon.

    I've never had any component of the BCG too hot to handle.

  3. #13
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    I think one major difference that I notice is barrel heat.

    In a DI system the heat gets to travel to the bolt where it can cool off

    while in a piston system.. the heat has no where to go but stay in the barrel.
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  4. #14
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    on an added note...

    heat shields
    free float alum handguard
    attachments to the barrel

    these things can affect the coolness of a barrel


    There was a piston gun that I saw which attached a heat sink at the base of the barrel. which made me think...

    I think it was a POF. why did the engineer put heat sinks there? he probably knew the barrel was hotter than normal.
    Last edited by lanceriley; 07-08-10 at 20:16.
    www.cpra.ph
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  5. #15
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    From my limited testing and experience, I found that the HK416 barrel remained consistently cooler than the barrel on the M4. Whether this is a result of barrel length, added heat sink barrel nuts, etc. I don't know.

  6. #16
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    HK416 has a rail right?

    m4 system we are talking about does it have a rail?


    assuming that both barrels are of the same length and of the same diameter and of the same material. Both barrels as they were without DI or Piston system should heat up in the same way and cool off in the same way.


    the more metal you add on a system for heat to travel to results in more "open" metal exposed to air. dissipating it's heat. hence aluminum handguards and heat sinks help. but it's not the pison system.

    there is more metal in a bolt compared to a Piston gas block. the movement of the piston also helps in cooling it off. As the heat travels to the rear in a DI. you are also heating the upper receiver which is aluminum... which also dissipates quickly due to it's being aluminum. in a piston system. heat is stuck up to the gas block. you only have the barrel and the gas block metal to dissipate the heat to. unless... you add more aluminum like a heat sink and a rail.
    www.cpra.ph
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  7. #17
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    HK416 is the 10" variety. The Colt is a standard USGI-type 14.5" barrel with a Knight's RAS installed.

    An additional test that might prove interesting would be to shoot several guns and then measure temps at set increments until the guns have returned to air temperature.

  8. #18
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    the best way to test is using 2 guns with the same length and barrel diameter.


    otherwise the argument would be which barrel is cooler? a shorter barrel or a longer barrel?

    or it could be barrel material difference? or it could be which handguard is cooler?

    to make it less subjective. all handguards should be removed.
    www.cpra.ph
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  9. #19
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    The HK rail doesn't touch the barrel except where it interfaces with the barrel nut and upper.

  10. #20
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    yes all free floatrails touch only atthe point of attachment. nevertheless. there is still heat transfer .
    www.cpra.ph
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