Author Topic: AR Ammo & Barrel Twist Rate  (Read 260 times)

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Offline Libertas

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AR Ammo & Barrel Twist Rate
« on: February 21, 2017, 07:40:07 AM »
http://www.captainsjournal.com/2017/02/19/ar-15-ammunition-and-barrel-twist-rate/

I'm going to have to look into this in more detail, to be honest off the top of my head I cannot recall examining this aspect too closely.

Hopefully others find it useful too.
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Offline Glock32

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Re: AR Ammo & Barrel Twist Rate
« Reply #1 on: February 21, 2017, 09:32:03 AM »
Most interesting.  I normally shoot M193-type ammo in my ARs, and I long wondered about whether their 1-7 twist was too rapid for those light 55 grain bullets.  These are the same bullets that were adequately stabilized in Vietnam-era M16s and their 1-12 twist rate.

My concern was never about accuracy, though.  If they were wildly inaccurate from a 1-7 barrel I probably would have noticed that.  My concern was if an overly stabilized projectile would tend to drill through a target (ice pick wounds) rather than the yawing and tumbling that improves lethality.  The M193 in Vietnam was known to be devastating against unarmored enemy personnel, and a lot of that was attributed to its relatively slow 1-12 twist.

For better or worse though, 1-7 is the military standard for over 30 years now.  You would think ammo makers would optimize their bullets for that twist rate.  I am probably going to start trying more of the 69-77 grain ammo.
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Offline Libertas

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Re: AR Ammo & Barrel Twist Rate
« Reply #2 on: February 21, 2017, 11:30:38 AM »
With M855 they had this chart...



Largest yaw rate is in the CQB range, which also could be called the novice range since most inexperienced rifle shooters will be short range shooters by default...all it takes is one poor attempt out further to do nothing but tell a badder animal a crappy shot with guns and ammo is just a football field away...

But they do say the best thing to do is practice with what you have and get proficient with it, which is always good advice.  I need to scuba to the bottom of the lake though if I want some practice time in!
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Offline Glock32

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Re: AR Ammo & Barrel Twist Rate
« Reply #3 on: February 21, 2017, 11:47:37 AM »
My problem is I very seldom have a chance to shoot rifles, and even then it's almost never at range more than 30-40 meters.  I envy those guys on YouTube able to blast hundreds of rounds at a time out on farmland somewhere.
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Offline Libertas

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Re: AR Ammo & Barrel Twist Rate
« Reply #4 on: February 21, 2017, 11:54:28 AM »
Yeah, I got to work a deal with somebody somehow...rent some land...or buy some...something...I wanna go Hickock45 on some stuff and push out some hundreds of yards with a rifle!
Irrumabo!  GOP? - Nope. No more. They made their bed, now let them die in it.*
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