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Thread: Any reason not to use a 1/12 twist 16" barrel if limited to M193?

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    Any reason not to use a 1/12 twist 16" barrel if limited to M193?

    If I built an AR that would be fed EXCLUSIVELY with M193 is there any reason I should NOT use a 1/12 twist 16" barrel?

    Is there any benefit to doing so, such as possible increase in velocity or terminal effect?

    Thanks

    TED

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    There's no practical difference in velocity or terminal performance between barrels with 1/7 or 1/12 twists.

    Rounds fired from a 1/12 twist barrel start off at a lower rpm and start losing stability at a shorter range. I don't know at what yardage that would be or if it makes any practical difference.
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    Quote Originally Posted by TED View Post
    If I built an AR that would be fed EXCLUSIVELY with M193 is there any reason I should NOT use a 1/12 twist 16" barrel?

    Is there any benefit to doing so, such as possible increase in velocity or terminal effect?

    Thanks

    TED
    Why paint yourself into a corner? However, if you plan to use FMJ ammo for self defense, the slower twist might allow the bullet to yaw after impact and fragment causing more damage than a stabilized bullet passing through leaving a .22 hole. But no, in today’s world I would never want a 1/12 twist.

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    Quote Originally Posted by MistWolf View Post
    There's no practical difference in velocity or terminal performance between barrels with 1/7 or 1/12 twists.

    Rounds fired from a 1/12 twist barrel start off at a lower rpm and start losing stability at a shorter range. I don't know at what yardage that would be or if it makes any practical difference.
    A regular child's top spun by hand and spinning on a table top, takes about 5 to 10 seconds before it shows signs of instability. So accounting for the difference in angular moment of inertia, angular speeds and drag from the table, the average bullet will probably remain stable for 5 to 6 seconds when spun at 180,000-200,000 rpm.

    So, how far will a bullet go in 5 to 6 seconds?
    Last edited by lysander; 01-15-21 at 22:47.

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    Quote Originally Posted by lysander View Post
    A regular child's top spun by hand and spinning on a table top, takes about 5 to 10 seconds before it shows signs of instability. So accounting for the difference in angular moment of inertia, angular speeds and drag from the table, the average bullet will probably remain stable for 5 to 6 seconds when spun at 180,000-200,000 rpm.

    So, how far will a bullet go in 5 to 6 seconds?
    Oh dang

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    It will be stable. I think the better question is “why go with a 1:12” twist?”

    The answer, I can’t think of a reason.


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    Only reason I can think of is if you are going to be shooting a lot of .22 rimfire, the 1/12 is closer the the .22's 1/16 so should in theory give better accuracy.
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    It will perform tolerably with 193, probably gonna see more drift as range steps out.

    Can you explain why you would choose to limit your ammo selection and settle for "meh" from your rifle?
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    You guys do realize the 1/7 is a pretty crappy twist rate that was only picked to stabilize super long M856 tracer in extreme low temperature. Kind of a shame it became the default for civilians instead of something like 1/8 or 1/8.5.
    “The Trump Doctrine is ‘We’re America, Bitch.’ That’s the Trump Doctrine.”

    "He is free to evade reality, he is free to unfocus his mind and stumble blindly down any road he pleases, but not free to avoid the abyss he refuses to see."

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    Quote Originally Posted by mack7.62 View Post
    You guys do realize the 1/7 is a pretty crappy twist rate that was only picked to stabilize super long M856 tracer in extreme low temperature. Kind of a shame it became the default for civilians instead of something like 1/8 or 1/8.5.
    What is crappy about it? What does it do poorly?


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