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Thread: Measuring the barrel gas port size

  1. #51
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    Quote Originally Posted by Clint View Post
    Tested one size smaller insertable gas port.
    Dropped down to .073"
    ... Do want.
    We miss you, AC.
    We miss you, ToddG.

  2. #52
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    For us of small minds...

    Which manufacturers of carbines and uppers provide 'PROPER' gas port diameters for their carbine length gas systems???

  3. #53
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    Quote Originally Posted by MK18Pilot View Post
    Photos or it doesn't exist...
    Quote Originally Posted by Magic_Salad0892 View Post
    ... Do want.
    This has been tested with a low pro gas block but not a FSB yet.

    This may also be usefull for a dedicated suppressed setup made with a standard barrel.
    Last edited by Clint; 10-14-11 at 11:50.
    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

  4. #54
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    Quote Originally Posted by Clint View Post
    This has been tested with a low pro gas block but not a FSB yet.
    Even better.
    We miss you, AC.
    We miss you, ToddG.

  5. #55
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    Very informative thread!

    I may have missed it but is there an "ideal" gas port size for a 16" mid-length barrel?

    It was mentioned in this thread that Colt carbines have a gas port size of between .062 and .064. Does anyone have the gas port sizes on a Colt 20" barrel?

    I would also be interested to know if there a difference between the gas port sizes Colt's 14.5 and 16"carbine barrels.

  6. #56
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    Quote Originally Posted by m4brian View Post
    For us of small minds...

    Which manufacturers of carbines and uppers provide 'PROPER' gas port diameters for their carbine length gas systems???
    Colt, LMT, BCM, Noveske (they don't make 16" carbines anymore, IIRC), DD.
    Why do the loudest do the least?

  7. #57
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    Found what looks to be a reliable data point on the 10.3" Mk18 from

    http://en.wikipedia.org/wiki/Close_Q...attle_Receiver

    Quote Originally Posted by WIKI
    The short 10.3 in (262 mm) barrel length requires special modifications to reliably function. The gas port is opened from 0.062 to 0.070 in (0.16 to 0.18 mm). A one-piece McFarland gas ring replaces the three-piece gas ring set. The standard four-coil extractor spring is replaced with a commercial off-the-shelf (COTS) five-coil spring. An O-ring surrounds the extractor spring. The standard M4 flash hider has been replaced with the M4QD flash hider for suppressor compatibility.
    This seems to match closely with Robb's info here>
    https://www.m4carbine.net/showthread.php?t=74292
    Last edited by Clint; 10-13-11 at 23:48.
    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

  8. #58
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    Quote Originally Posted by m4brian View Post
    For us of small minds...

    Which manufacturers of carbines and uppers provide 'PROPER' gas port diameters for their carbine length gas systems???
    Colt
    BCM
    Noveske
    DD
    LMT
    KAC

    There maybe others, but the above are the low fruit.



    C4

  9. #59
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    Relative my earlier posts, I'm thinking or ordering this set.

    According to dealer:
    Increments of .001"
    total of ~190 pins
    Last edited by rob_s; 10-14-11 at 10:15.

  10. #60
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    Quote Originally Posted by rob_s View Post
    Relative my earlier posts, I'm thinking or ordering this set.

    According to dealer:
    Increments of .001"
    total of ~190 pins
    Unless you have a bunch of other things that you want to gauge, I would just focus on diameter specifications of the holes you want to measure, and order just under to ~.010" over, in appropriate steps.

    If limited to ARs, I can think of gas ports and FCG hole diameters maybe, but not much else. There are places where you can order just specific, individual guages at ~$2-2.50/pin, and you'll come out $$ ahead. Otherwise, spend the $60, get a complete set like you're looking at, and then realize the bulk of those pins will never be used, unless you have other measuring requirements for non-ARs. Just another option to consider.

    http://www.auto-met.com/gage/pin_gage.htm

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