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Thread: I Think It's Under-Gassed?

  1. #11
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    Quote Originally Posted by cheeta View Post
    ... I read the barrel descriptions from several suppliers like Daniel Defense, they open up their 16" carbine barrel's gas ports to .075"...
    I'm curious where you saw that. It's hard to believe DD would open up the gas port that wide over the norm of .063". And if we're talking a midlength gas system you'd expect something more like .059".

  2. #12
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    Quote Originally Posted by Quentin View Post
    I'm curious where you saw that. It's hard to believe DD would open up the gas port that wide over the norm of .063". And if we're talking a midlength gas system you'd expect something more like .059".
    Keep in mind that the further the distance from the chamber to the gas port, the lower the pressures and will require a larger sized gas port to operate the rifle. I believe the port of a rifle length gas system is .092"
    Last edited by MistWolf; 01-13-11 at 05:16.

  3. #13
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    Interesting thread. Does anyone know definitively what the port size is on an SR15?

  4. #14
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    Thanks for all your replies and patience.

    That storm had me busy at work.

    I'll not be giving out manufacturers names because I'm sure it doesn't matter relating to my functioning problem(s).

    I've got parts swapping to do at the range first between known reliable stuff and the stuff on my newest creation to trouble-shoot specific parts and assemblies.

    I'll be trying a piece of flexible vinyl tube tightly fit over the end the gas tubes of both the known good rifle and the new problem child and giving them a good puff and comparing how air moves through them.

    I was hoping someone had a quick solid number--??? of an inch diameter gas-port-- gave the best all-around functioning with most civilian ammo out of a 16" carbine.

    I promise to keep you guys updated, it's just that I'm a bit busy.
    Last edited by cheeta; 01-13-11 at 19:02. Reason: Edit to add:

  5. #15
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    Quote Originally Posted by MistWolf View Post
    Keep in mind that the further the distance from the chamber to the gas port, the lower the pressures and will require a larger sized gas port to operate the rifle. I believe the port of a rifle length gas system is .092"
    My understanding is that Colt uses .088 on rifles.

  6. #16
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    Leave the gas port as is. I highly doubt that's the cause of your problems. As suggested above, check your gas key. Most importantly for now, since you mentioned thatthis is a stripped barrel build, check the alignment of your gas block.
    When you have the time, give us a complete breakdown of the entire build.

  7. #17
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    Actually the manufacturer has ALOT to do with it. If you want our help provide the information. If not, then continue to roll the dice until you figure it out.

    All AR's are not created equally and they vary across the board.

    Quote Originally Posted by cheeta View Post
    Thanks for all your replies and patience.

    That storm had me busy at work.

    I'll not be giving out manufacturers names because I'm sure it doesn't matter relating to my functioning problem(s).

    I've got parts swapping to do at the range first between known reliable stuff and the stuff on my newest creation to trouble-shoot specific parts and assemblies.

    I'll be trying a piece of flexible vinyl tube tightly fit over the end the gas tubes of both the known good rifle and the new problem child and giving them a good puff and comparing how air moves through them.

    I was hoping someone had a quick solid number--??? of an inch diameter gas-port-- gave the best all-around functioning with most civilian ammo out of a 16" carbine.

    I promise to keep you guys updated, it's just that I'm a bit busy.



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  8. #18
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    Quote Originally Posted by Iraqgunz View Post
    Actually the manufacturer has ALOT to do with it. If you want our help provide the information. If not, then continue to roll the dice until you figure it out.

    All AR's are not created equally and they vary across the board.
    If I'd have known you were so uptight about it I wouldn't have posted. Cheeezz!

  9. #19
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    No one is being uptight about it. All that is being said is that not all AR part manufacturers are the same. If you tell us what you used we may be able to help you pin down a part by a problematic manufacturer.

    I've done it. I cheaped out on my build at first with a blackthorne complete upper. Ended up with issues cause at least partially by substandard parts. My upper is now completely different and built with components from quality companies and it runs like a champ.

  10. #20
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    Look at it this way. Its like you are going to a car forum and saying my custom built Chevy won't start, what's wrong with it? Then not giving any more information about the car.

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