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Thread: Gas port sizes?

  1. #1
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    Gas port sizes?

    Is there a list somewhere of the "standard" gas port sizes on carbine and rifle length gas systems, AR10 and LR-308 would be good, too.

    What is the "perfect (M16 length)" gas pressure needed at the port?

    Better yet, is there a formula to get the hole size right?

    I'm building a wildcat with an extended length tube and hate to do a "Just drill one and try it out, repeat" I'm putting on an adjustable gas system, but want to get the hole close.

    I have Quickload and can figure approx. pressures at different locations on the bbl.

    Any info would be appreciated.

  2. #2
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    Quote Originally Posted by Lostinthewoods View Post
    Is there a list somewhere of the "standard" gas port sizes on carbine and rifle length gas systems, AR10 and LR-308 would be good, too.

    What is the "perfect (M16 length)" gas pressure needed at the port?

    Better yet, is there a formula to get the hole size right?

    I'm building a wildcat with an extended length tube and hate to do a "Just drill one and try it out, repeat" I'm putting on an adjustable gas system, but want to get the hole close.

    I have Quickload and can figure approx. pressures at different locations on the bbl.

    Any info would be appreciated.

    Mil-standard for a carbine (14.5/16) is .063. Only your mil-spec manufacturers are going to use this size (Colt, BCM, Noveske, DD, etc). Middy's tend to vary greatly as there is no TDP for them.

    If you are using a high pressured load and a 16" barrel, go with a middy gas system for sure. Drill the hole small and see if you get bolt lock back. If not, then drill a bigger hole and try again.


    C4

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    Quote Originally Posted by C4IGrant View Post
    Mil-standard for a carbine (14.5/16) is .063. Only your mil-spec manufacturers are going to use this size (Colt, BCM, Noveske, DD, etc). Middy's tend to vary greatly as there is no TDP for them.

    If you are using a high pressured load and a 16" barrel, go with a middy gas system for sure. Drill the hole small and see if you get bolt lock back. If not, then drill a bigger hole and try again.


    C4
    Is it safe to re-drill the gas port?

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    Quote Originally Posted by tonnete_r View Post
    Is it safe to re-drill the gas port?
    Is it the best option? No, I don't think so, but I don't think you will cause any serious harm.


    C4

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    Thanks Grant, have any idea of hole size on AR10 20" bbl?

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    I agree with Grant. If absolutely necessary, it can be done without any harm. I think it should be a last resort though. You also need to make sure its done by someone who knows what he's doing.
    Ive seen this procedure go bad a couple of times.

    Last edited by Col_Crocs; 11-18-09 at 21:28.

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    Quote Originally Posted by Col_Crocs View Post
    I agree with Grant. If absolutely necessary, it can be done without any harm. I think it should be a last resort though. You also need to make sure its done by someone who knows what he's doing.
    Ive seen this procedure go bad a couple of times.

    Can you give me a refernce for the said measurements, I think I have some useful application for this.

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    IMHO all those port sizes are too large. Might be fine for commerical .223 pressure ammo but too big for 5.56mm NATO pressure ammo.
    Chief Armorer for Elite Shooting Sports in Manassas VA
    Chief Armorer for Corp Arms (FFL 07-08/SOT 02)

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    Quote Originally Posted by gotm4 View Post
    IMHO all those port sizes are too large. Might be fine for commerical .223 pressure ammo but too big for 5.56mm NATO pressure ammo.
    Agree.



    C4

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    Quote Originally Posted by C4IGrant View Post
    Agree.



    C4
    What are the correct diameter?

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