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Discussion Starter · #1 ·
What's the story on all the 1:10" twist rates?

Just curious about one criticism about the XCR barrels mentioned on another forum. A poster pointed out that all the current barrels have a 1:10" twist, and said it was a definite negative.

1:10" seems less common than 1:9" .223 ARs these days. As I understand it, 1:9" is common, and 1:7" is popular for stabilizing some of the popular fighting rounds over 62gr.

1:10" seems common enough for 7.62x39mm, though glancing around I'm seeing all kinds of twist rates mentioned for AKs.

For 6.8SPC, I've read a lot of threads claiming that it's simply too fast for many of the good 6.8 loadings, and that velocity and performance are quantifiably better with 11, 12, and 13".


So is the 1:10" thing for the sake of convenience and keeping costs down, or is it a definite choice by RA based on the rounds likely owners will use? Would it add much expense to do different twists, or is it simply a matter of typing a different number into a machine?
 

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Re: What's the story on all the 1:10" twist rates?

A 1:10" twist barrel, I have never seen that in a 5.56mm. Normally 6.8mm and up to 7.62x39 and 7.62NATO. Yes I had an AR with a 1:12" twist. That was my M16a1 clone (semi only). And I used mostly 55gr stuff. I did use 62gr stuff also but long range (100+ yards), just don't work.
 

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Re: What's the story on all the 1:10" twist rates?

Both my 5.56 barrels are 1:9" and I believe the 6.8 is 1:10". There are a few 1:8" barrels floating around out there too. They don't use a set twist, it is dependant on the caliber.
 

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Discussion Starter · #4 ·
Re: What's the story on all the 1:10" twist rates?

Both my 5.56 barrels are 1:9" and I believe the 6.8 is 1:10". There are a few 1:8" barrels floating around out there too. They don't use a set twist, it is dependant on the caliber.
The reason it came up is that the official XCR site says 1:10" for everything but the (not fielded) 6.5.

Is this info not accurate, or have they moved to 1:10"

http://www.robarm.com/XCR_Cal_Conversion_Specs.asp
 

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Re: What's the story on all the 1:10" twist rates?

The 5.56's are in 1:9, I ahve one of the very early 1:8 HBAR's. I believe the 6.8 are in 1:10
 

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Re: What's the story on all the 1:10" twist rates?

if the website is saying the 5.56 is 1/10, it's an Alex-made-a-website-blooper
 

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Discussion Starter · #7 ·
Re: What's the story on all the 1:10" twist rates?

Yup, the website does indeed say 1:10", in the Conversion section as I linked to above.

What is the actual current twist of the 5.56mm? Is there really much reason not to use 1:7 these days, since practically nobody shoots anything lighter than 55gr in a combat-type rifle? Or is it a slower twist for the small number of folks who want to varmint with 45gr in their XCR?
 

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Re: What's the story on all the 1:10" twist rates?

All the current 5.56 barrels are 1:9. 1:9 is the most versatile 5.56/.223 twist. You can shoot everything from ~45gr to ~70gr. Only the heaviest 5.56 mag length loadings (77gr) can not be shot reliably in the 1:9. In a 1:7, you are typically not advized to shoot anything less than 55gr. In my experience, with 55gr, I have seen cumulatively better accuracy from all the 1:9 rifles I have owned than I have seen from all the 1:7's. I own several 1:7 AR's, so personally, having only 1:9 available on the XCR is not a big deal to me; that said, I do agree it would be nice to have a 1:7 option, and I would buy a barrel in that twist if they offered it.

Twist rates between calibers are not really comparable. I will defer to the 6.8 experts here to tell you the pluses and minuses of different 6.8 twists.
 

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Re: What's the story on all the 1:10" twist rates?

THIS IS A WEBSITE TYPO!!! OUR 5.56'S ARE ALL 1/9 THE 6.8'S AND THE 762'S ARE 1/10. I'LL HAVE IT FIXED ON THE WEBSITE
 

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Re: What's the story on all the 1:10" twist rates?

0000033740 said:
1:10 Twist in 6.8 from Rob arms and LWRC will shoot the best and hottest SSA ammo, which is the best 6.8 ammo out right now.
That's not my understanding: SSA had to go from calling their hottest loading "combat" to something else ("Tactical" I believe) b/c LWRC has close ties with SSA and their 1:10 twist couldn't handle the hotter loads without showing pressure signs....so they had to load it lighter.

RA is supposedly working on going to a 1:11 or possibly a 1:12 twist bbl (I'm assuming RA will keep the 4 groove bbl and SPC II chamber)....when they make the change, I WILL order. Until then though....I'll wait on a conversion.

Sean
 

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Re: What's the story on all the 1:10" twist rates?

hmm, usually twist rates for mass produced guns are for the mass produced ammo. As far as Ak's go, mine has a 1-11 twist, all my AR's have had 1-8 or 1-9, i will probably build a custom bolt gun with a custom turned barrel so i can match twist rate with a particular grain ammo. I don't know how ordering works for you guys, but where i order XCR's i get a choice of what barrel to put in along with many other options, just not a package deal someone put together for me.
 
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