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

  1. #11
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    Quote Originally Posted by Serious Account View Post
    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?
    In short, NO.

    One goal for any combination is a consistent carrier velocity and cyclic rate.

    If the reciprocating mass is constant, a similar cyclic rate requires the same total gas drive.


    The combination of gas system length and barrel length dictates which portion of the overall pressure curve is used to cycle the system.

    The gas port size then scales down this portion, resulting in the total gas drive.


    In general, shorter gas systems require smaller gas ports to produce the same total gas drive.

    In your example, a 14.5 MID with an .080" gas port has approximately the same gas drive as a 14.5 CAR with an .065" gas port.

    These two configurations will behave a little bit differently due to the differences in timing, but the overall cycling will be similar.

    Its interesting to note that either configuration can be optimally gassed, under gassed or over gassed, depending on the gas port size relative to what is optimal for each configuration.
    Last edited by Clint; 11-03-15 at 21:24.
    Black River Tactical
    BRT OPTIMUM HFCL Barrels - Hammer Forged Chrome Lined 11.5", 12.5", 14.5"
    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"
    BRT MicroTUNE Adjustable Gas Blocks
    BRT CustomTUNE Gas Ports

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