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Thread: Gas Piston weight

  1. #11
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    Exclamation

    With a loaded mag, this baby (POF-415 Gen.III) tipped the scales @ almost 11lbs, in 2009.




    That's why my current HD rifle, weighs just under 7lbs - loaded.





    Piston rifle was fun, it was different, it was cool, it got a lot of attention... and it damn near killed me at a couple of carbine classes

    I'm 12 years older, & slower now. The main thing a piston rifle taught me was - get a LIGHTER rifle!!!
    - Either you're part of the problem or you're part of the solution or you're just part of the landscape - Sam (Robert DeNiro) in, "Ronin" -

  2. #12
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    FWIW, I have a PWS Mk116 Mod 2 that weighs 6 lbs 8 oz naked. Has a tapered medium profile barrel and the long stroke gas piston. Even has a 15" handguard. Pretty light for a piston AR.
    “You have made us for yourself, O Lord, and our heart is restless until it rests in you.” -Augustine

  3. #13
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    Gas Piston weight

    Thanks for the piston info. Back on topic. Let’s put the piston into context with actual data:

    A midlength gas tube weighs 0.8 oz.

    An LMT piston (regulator, piston, and spring) weighs 3.4 oz.

    A difference of 2.6 oz.

    A full rifle weighing 112 oz (7lbs), the difference in weight amounts to around 2%.

    For reference:

    BCM shorty MLok grip - 1.9 oz (~1.5%)

    Difference between medium contour and light weight barrel (from BCM) - 6 oz (~5%)

    Difference between LMT sopmod stock and BCM gunfighter stock - 4 oz (~3.5%)

    In conclusion: The use of a piston systems weight penalty is in line with most other common AR accessories and build choices. It isn’t excessively heavy when put into perspective. Are the benefits worth the weight? That’s a question I can’t answer.


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    Last edited by Kyohte; 02-18-21 at 13:53.

  4. #14
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    The differences in weight should also include the gas block.

    Piston gas blocks tend to be the heavier.

    The standard FSB is pretty heavy at 4.8 oz.

    A low profile DI gas block is pretty light at 1.4 oz.
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  5. #15
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    Gas Piston weight

    Quote Originally Posted by Clint View Post
    The differences in weight should also include the gas block.

    Piston gas blocks tend to be heavier.

    The standard FSB is pretty heavy too, but low profile DI gas blocks are light.
    Good discussion. I’ve never delved into piston weight before.

    True, but I don’t have any to weigh. I only have piston experience in 5.56 with LMT. I can’t imagine between an LMT and fixed FSB being significant since piston gas blocks are bored out for the piston and regulator. A low profile I would suspect would be maybe an 1-2 oz lighter. Basically the difference between a fixed and low profile, which I never see brought up in weight discussions. Piston carriers will be slightly lighter too because of the lack of gas key and screws.

    Real world comparison:

    A Colt 6920 OEM-2 with LPVO, 13” BCM MCMR rail, etc etc weighs 9 lbs 5 oz. unloaded.

    An LMT MRP piston set-up similarly but with a 1 oz heavier stock, 1 oz heavier scope, and 1 oz heavier light mount weighs 10 lbs exactly.

    So 11 oz difference between the rifles that isn’t accounted for in accessories. In DI, LMT MRP barrel is 2.3 lbs, gov profile Colt is 2 lbs both with FSB. That accounts for 4.8 oz in barrel profile.

    So overall, it appears the piston is adding a bit over 1/4 lb (4 oz). That’s not insignificant, but it isn’t making the piston a boat anchor like a lot of people seem to believe.


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    Last edited by Kyohte; 02-19-21 at 07:53. Reason: Clarification of some measurements

  6. #16
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    Quote Originally Posted by georgeib View Post
    FWIW, I have a PWS Mk116 Mod 2 that weighs 6 lbs 8 oz naked. Has a tapered medium profile barrel and the long stroke gas piston. Even has a 15" handguard. Pretty light for a piston AR.
    I run the MK111 in 7.62x39 crazy light enough for me.

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