How important is the rate of twist?
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Old 08-04-2010, 03:25 AM   #1
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Default How important is the rate of twist?

I always see the different twist rate on barrels but how important is it really? I mean how much real world difference would you see when comparing a 1:9 barrel and a 1:7 barrel?

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Old 08-04-2010, 03:40 AM   #2
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Depending the grain of bullet you are shooting, it can make a big difference.

If you are building a 16", Minute of Bad Guy, across the street gun in the event of SHTF, you are probably safe with either.

Want to shoot out to 100 yards and hit smaller targets? You better get the right twist rate for the bullets you are going to run.

JD

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Old 08-04-2010, 03:45 AM   #3
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It makes a lot of difference when it comes to being able to stabilize different bullet weights. There's not that much difference in a 1-7/1-9 until you start wanting to shoot 77gr or bigger bullets,but the 1-7 in some barrels doesn't like lighter bullets 50gr or smaller.

I have a 1-8 twist in both my AR's and shoot 55-80gr bullets out of both very well.

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Old 08-04-2010, 04:06 AM   #4
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What twist rate would be ideal for a 55gr bullet?

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Old 08-04-2010, 05:10 AM   #5
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Originally Posted by BigSe63xy View Post
What twist rate would be ideal for a 55gr bullet?
Ideal would be the original design...1:12, but then you will be limited to an upper weight of about 62gr or so. Ideal specs never function well in the commercial markets, that's why most generally available ARs will have a 1:7 or 1:9 barrel. It's a compromise between optimum performance and marketing and covers a wider range of bullet weights satisfactorily but not ideally.
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Old 08-04-2010, 02:52 PM   #6
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Default How important is the rate of twist?

A slow rate of twist will not properly stabilize a LONG (ie. "heavier") bullet, and it will tumble on it's way toward the target instead of spiraling like a football.

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Old 08-04-2010, 08:03 PM   #7
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Could 1:7 handle even a lighter bullet?

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Old 08-04-2010, 11:22 PM   #8
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Could 1:7 handle even a lighter bullet?
Lighter than what, 55 gr.? Possible but not going to be reliable 100% of the time. Many rounds will just disintegrate right out of the barrel.

What ammo do you have in mind, what are you intending to use the rifle for, i.e. varmint control, plinking, distance shooting, SHTF all purpose. It would be easier to offer assistance if you described what you had in mind, what situations you intend to use the gun for, are you looking for a purpose built or all around type setup?

With some more info folks can offer suggests or share their experiences.
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Old 08-05-2010, 01:01 AM   #9
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1:9 is pretty hard to beat for the average shooter since it tends to be ideal for 50-62gr ammo which is the cheapest and most common in stores. It can work from 45-69 gr or more but you'd want to test the ammo in that individual barrel before buying a lot. 1:8 can do well over a wide range too.

1:7 or 1:12 are good if most of your shooting is out of that range above, with 1:7 ideal for 62-77+ and 1:12 for under 50gr.

Of course there is overlap and each barrel is different so you pick one and hope it covers the range of ammo you'll likely use.

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