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Thread: Does mid-length AR require H2 buffer to function reliably in full-auto?

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    Does mid-length AR require H2 buffer to function reliably in full-auto?

    I'm curious. The M4A1 has a H2 buffer to eliminate (or reduce) 'bolt-bounce' when firing in full auto, but does mid-length gun require H2 buffer to function reliably when fire in full-auto as well? How well does mid-length gun perform in full auto using only "H" buffer? Have they ever been tested extensively with full-auto fire to the same extend that the M4A1 had?
    Last edited by Serious Account; 10-28-15 at 14:11.

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    Quote Originally Posted by Serious Account View Post
    I'm curious. The M4A1 has a H2 buffer to eliminate (or reduce) 'bolt-bounce' when firing in full auto, but does mid-length gun require H2 buffer to function reliably when fire in full-auto as well? How well does mid-length gun perform in full auto using only "H" buffer? Have they ever been tested extensively with full-auto fire to the same extend that the M4A1 had?
    I think the answers to your questions would largely depend on the gas-port size/barrel length of the mid-length and the ammo used.

    To my knowledge, there are no mid-length guns used by the US military, so I think it's fair to say that there has not been extensive testing with FA.
    Last edited by scooter22; 10-28-15 at 14:35.

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    I'll give you this: if you get bolt bounce in your m16, with hammer down and a light primer strike, try a heavier buffer.

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    Bolt (carrier) bounce happens on return to battery and has relatively little to do with the gas system length.

    Higher carrier speeds from over gassing or heavy action springs will tend to make the bounce worse.

    Lots of high speed video has been shot of this and the effect of various buffer weights and systems has been recorded.

    Heavier ( 4.6-5.4 oz ) H2/H3/A5 buffers have shown to do a much better job at taming bounce.
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    I have used an H1 buffer with a Noveske n4 16" midlength on my M16 lower. It runs great. I currently use a h2 buffer as this allows me to swap between 10.5", 14.5", and 16" uppers.

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    Thanks all for the quick replies. I always thought that "H2" buffer generally don't work well with mid-length. Correct me if I'm wrong but even BCM and DD recommend to NOT use anything heavier than H buffer for mid-length gun (especially 14.5 in middy) - can anyone here confirm this?.

    It would be really great if there's a torture test for mid-length gun firing in Full Auto or a full auto test with both H and H2 buffer
    Last edited by Serious Account; 10-31-15 at 05:03.

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    There is no standard or TDP for a midlength carbine. I have seen gas ports as low as .074 up to .086, so gas port size is definitely part of the equation. As a general rule, I measure every single barrel unless I know the port in advance.

    Before swapping everything to the A5, I ran my 16" .076 gas port middy with an H2 and blue Sprinco spring and never had malfunctions. I do not shoot crappy or reloaded ammo. I also lube my stuff generously as well.

    Quote Originally Posted by Serious Account View Post
    Thanks all for the quick replies. I always thought that "H2" buffer generally don't work well with mid-length. Correct me if I'm wrong but even BCM and DD recommend to NOT use anything heavier than H buffer for mid-length gun (especially 14.5 in middy) - can anyone here confirm this?.

    It would be really great if there's a torture test for mid-length gun firing in Full Auto or a full auto test with both H and H2 buffer



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    Quote Originally Posted by Iraqgunz View Post
    There is no standard or TDP for a midlength carbine. I have seen gas ports as low as .074 up to .086, so gas port size is definitely part of the equation. As a general rule, I measure every single barrel unless I know the port in advance.
    Before swapping everything to the A5, I ran my 16" .076 gas port middy with an H2 and blue Sprinco spring and never had malfunctions. I do not shoot crappy or reloaded ammo. I also lube my stuff generously as well.
    That's the key post here and why there's no answer to this question. It's one I get daily from viewers and they're always frustrated when I answer "it depends..." but it does.

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    Quote Originally Posted by Serious Account View Post
    Thanks all for the quick replies. I always thought that "H2" buffer generally don't work well with mid-length. Correct me if I'm wrong but even BCM and DD recommend to NOT use anything heavier than H buffer for mid-length gun (especially 14.5 in middy) - can anyone here confirm this?.

    It would be really great if there's a torture test for mid-length gun firing in Full Auto or a full auto test with both H and H2 buffer
    I like to standardize on A5H2, Rifle or H2 buffer weights for all lowers and then run a variety of uppers interchangeably.

    If a quality upper won't run on that lower, the gas port size needs to be adjusted.

    Some 14.5" middys may have gas ports just a tiny bit smaller than needed to run 100% with those buffers.


    Speaking broadly, most ( 95% )barrels seem to have gas ports that range from "correct" to "way over gassed".

    Those will almost always take a heavy buffer.

    Occasionally (5%) , a barrel with have a gas port that is too small to run a heavy buffer and/or .223 ammo.

    Bumping up the gas port a size or two takes care of it.


    Just saying xxx about middys is not specific enough.

    It all depends on the specific combination of barrel length, gas system length and gas port size.

    A 12.5" MID runs quite differently than an 18" MID.

    Same thing with a 10.5" CAR vs 16" CAR.
    Last edited by Clint; 10-31-15 at 20:31.
    Black River Tactical
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    BRT OPTIMUM Barrels - 16" MPR, 14.5" MPC, 12.5" MRC, 11.5" CQB, 9" PDW
    BRT EZTUNE Preset Gas Tubes - CAR and MID
    BRT Covert Comps 7.62, 5.56, 6X, 9mm
    BRT MarkBlue Gas Tubes - BRT EXT, EXC and PDW Lengths
    BRT MicroPin Gas Blocks - .750" & .625"
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    Thanks again everyone I learned a lot here.

    I have another question, does enlarging the gas port of mid length guns kind of 'negate' the advantage of the mid-length, because you're going to direct as much gas into the system as the carbine system and therefore going to have the same recoil felt? Let's say for example, would a 14 in middy with .075 (or.080?) port size direct as much gas into the system as a carbine with .070 port size?
    Last edited by Serious Account; 11-03-15 at 18:00.

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