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Barrel Twist for AR-15


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I have two 1 in 9 twist barrels and have shot 75s in both.  One barrel (on a JP rifle) shoots them quite well (3/4 MOA), the other (a Douglas) shoots them ok ( 1 1/2 MOA).

Derrick martin says that a 1 in 9 will shoot anything you can put in the magazine including 77 sierras and 75 hornadys.   If you are going to exclusively shoot  bullets 68 grains and up, you may want a 1 in 7 but don't fret if you have a 1 in 9.

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If I was not going to shoot anything heavier than a 68-69 grains or lighter than 50-52 grains, I would choose a 1:9 twist. Like Kelly mentioned, the 1:9 should shoot pretty much anything you can put in the magazine, and IMHO would probably be the best all round choice.

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I agree with kelly.

I do not know of any decent 55gr match bullet, now I said that someone will sort me out. All the good ones are either 52-53 or start at 68 grain and go up. I have shot quite a few and would go with 1:9 or 1:10, I do lean more towards 1:9.

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after reading the post here  and in other place I understand why 1-9 for a barrel twist is ideal.

But then why would anyone want a 1/12 twist.   I was reading Les Baers web site and he offers his 223 top end with a 1/12 and other twist are optional.  

Why would someone spend alot of money on a top end only to get in 1/12?   thanks

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The benchrest shooters have proved to their satisfaction that onc eyou get a bullet stable "enough" then any more twist is bad for accuracy.  (Bad in the context of tenths of an inch at 100 yards.)

Someone who is a varminter, who will never put a bullet heavier than 53 grains down the bore, doesn't need any more than 1/12.

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  • 4 months later...

Some are of the opinion that 1 in 8 may be a good all-around choice for the reasons stated above, and due to recent trends toward heavier bullets.   1 in 8 ought to do okay at short range for the 55 grainers and do quite well with bullets into the 70s.  

Wonder what twist will go into the CARs if the gov't goes with a 100 grain bullet?    

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  • 2 weeks later...

I have done quite a bit of testing with a Bushy 16" 1-9 and Hornady 75 gr match.  I have had very good results with this combo shooting out to 500 m.  I would use a 1-8 or 1-7 for the heavy bullets, they stabilize much better.

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Mine has a 1x9 twist but I did not have the opportunity to try it at 300 meters.

I'll do it soon 'cause I have plenty of loads to try: 40s, 45s, 55s, 63s, 69s, 70s....

But I haven't found 75s through my smiths .

A friend of mine told me once that he have some 223 that appears to be much more heavy than the regular military loads, couldn't know the weight exactly, but He suppose they're around 90s or more.

Any of you ever heard about that ?

And last, but not least, please refresh my memory: SS109 = M855 , right ?

Thanks

DVC

Julien

Happy New year

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Julien, 77 gr bullets that can be loaded to work in magazines are popular in U.S. service rifle matches, as are 80 gr bullets, which can only be loaded long and hand-fed. There are heavier bullets but they are unusual. Supposedly the U.S. military is trying 100 gr bullets

Oui, SS109 and M855 are more or less the same, 62 gr steel tip penetrator bullet (green tip).

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