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Author Topic: AR-15 keyholing  (Read 12942 times)

RMc

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Re: AR-15 keyholing
« Reply #50 on: December 02, 2017, 04:23:05 pm »
Nope.  It's a 1 in 12.  See reply #16.

Indeed - extremely remote~ ;)
Alabama

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    Kaso

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    Re: AR-15 keyholing
    « Reply #51 on: December 02, 2017, 08:02:04 pm »
    Technically the cleaning rod measured 12-1/4" between one full rotation of the piece of tape.  Chances are, that was user error, or just the inaccuracy of the method.  There is the possibility that I pushed it 'in' some, rather than letting it only spin, but I don't think there was 2" worth.

    RMc

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    Re: AR-15 keyholing
    « Reply #52 on: December 02, 2017, 08:40:41 pm »
    Technically the cleaning rod measured 12-1/4" between one full rotation of the piece of tape.  Chances are, that was user error, or just the inaccuracy of the method.  There is the possibility that I pushed it 'in' some, rather than letting it only spin, but I don't think there was 2" worth.

    Agree: You are most likely right "on target" with your measurement of the twist rate.
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    Mississippi556

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    Re: AR-15 keyholing
    « Reply #53 on: December 05, 2017, 05:18:02 pm »
    Twist rate is rarely exactly what the nominal spec is stated to be.  A 1:12, which that certainly is, might be 1:12.25, and still be called 1:12.

    It should shoot 55 grain fmj and jacketed lead core just fine, but it will be limited to ammo like that.  Some really fine match .223 barrels are specifically rifled with 1:12 or even 1:14, especially when shooting lighter match grade flat base bullets, like the super accurate little Berger FB 52's.

    But, the barrel in question will not be very versatile.  Even if it shoots 55 grain bullets with good accuracy (likely) ammo has marched on and there is a trend in favor of longer bullets that simply will not stabilize in slow twist barrels, and it is hard to over-stabilize with too fast twist at .223/5.56 velocities.

    I've overstabilized 55 grain 6mm bullets before in a precision rifle, pushing them to over 4,100 fps.  The centrifugal force, (super high rpms from fast twist) literally separated the jackets from the core and the bullets exploded before reaching a 100 yard target.

    Velocities that high are not possible in the little .223 case, so no reason not to shoot even the lighter stuff in more versatile 1:8 or 1:7 twist barrels.

    All said and done, probably time to retire the old warrior barrel and upgrade to a tighter twist.
    Mississippi"When a strong man, fully armed, guards his own palace, his goods are safe"  Words of Jesus, Luke 11:21 (ESV).

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