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Thread: How to determine what the optimal gas port size would be?

  1. #1
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    How to determine what the optimal gas port size would be?

    Caliber is 6mm X 45, barrel length is 12.5"s and the DI gas system is carbine length. Barrel will have a .750 gas block journal.

    This rifle will be run 100 % of the time suppressed with an Omega .30 can.

    What I need to know is what gas port diameter to instruct the custom barrel maker.



    Barrel has arrived off to the range
    Last edited by 308sako; 02-28-18 at 08:33. Reason: Update of barrel's arrival
    Patriotism is supporting your country all the time, and your government when it deserves it. Mark Twain
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  2. #2
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    What we typically do for something like this is start with a known baseline and make judgment based adjustments for the other factors.

    The 6x45 will need a bigger port than 5.56, perhaps 15%.

    The omega is a 30 cal can, so its a lower back pressure can.

    Best guess is .0635" to start. That may or may not need to be bumped up.

    With something with this many variables, the final size needs to be determined after some testing.
    Black River Tactical
    BRT OPTIMUM Hammer Forged Chrome Lined Barrels - 11.5", 12.5", 14.5", 16"
    BRT EZTUNE Preset Gas Tubes - PISTOL, CAR, MID, RIFLE
    BRT Bolt Carrier Groups M4A1, M16 CHROME
    BRT Covert Comps 5.56, 6X, 7.62

  3. #3
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    Much appreciated, and I do think that starting smaller is far better than having too much gas to begin with.

    D
    Patriotism is supporting your country all the time, and your government when it deserves it. Mark Twain
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  4. #4
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    You could run your loads though QuickLoad to know the port pressure. That would probably help you dial in or verify your other estimates.

    advntrjnky

  5. #5
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    Good luck and let us know how it turns out.
    Black River Tactical
    BRT OPTIMUM Hammer Forged Chrome Lined Barrels - 11.5", 12.5", 14.5", 16"
    BRT EZTUNE Preset Gas Tubes - PISTOL, CAR, MID, RIFLE
    BRT Bolt Carrier Groups M4A1, M16 CHROME
    BRT Covert Comps 5.56, 6X, 7.62

  6. #6
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    Barrel arrived and the gas port is supposed to be and does mike out at .070" That's the smallest they would make, so test firing for cycling will commence shortly. A couple of basic ladders have been prepare with Nosler 55 grain Ballistic tips and Berger 68 grain match bullets. All at magazine length.

    More to follow.
    Patriotism is supporting your country all the time, and your government when it deserves it. Mark Twain
    Read more at: https://www.brainyquote.com/quotes/mark_twain_386139

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