Home Forums Hunting & Shooting AR and Tactical Rifles Twist Rate

I am new to the AR world
I have my rifle picked out with and 18” barrel but am struggling between 7:1 and 8:1 twist
I guess the vision is Winchester white box or similar coyote round and/or military style discounted fmj

Not as much heavy weight 77g or whatever

There is 1000 opinions out there already

Anybody have an opinion, ideally with test results
It seems the tests I have seen it doesn’t seem to make much difference

Thoughts?

I doubt you'll be able to tell any difference with any of the bullets that will fit in an AR magazine.

Play with the stability calculator at JBM Ballistics.

I have read that the only reason they went with 1/7 was to stabilize the tracer round.

But then we have all this 77, 75 and 73 grain stuff now and one would think the 1/7 would be better than 1/8 but I just don’t see it.

What I do see, and it may be a fluke but none of my 1/7 guns like the Hornady 75 HPBT ammo but 2 of my 1/8 guns and 1 of my 1/9 guns just love it.

And my 22-250AI bolt gun has a 1/8 that handles the 88 grain ELD’s just fine but obviously with more velocity.

For what you vision 8 will be fine. That said I have never found 7 to be a downside either. From 52 to 80s.

For a long time the AMU shot 7 twist instead of less. With 80s. They felt it just did better way out there. My tests mirrored theirs.

Really depends on what you want to run and what distance.

Personally I think 95% of people would never be unhappy with either the 8 or 9. We are in the other... if I can choose full 7 I run it, its always treated us right. But then 68 for the most part is light to me when I think 223 AR. 75 and up if possible. With the caveat of shooting long single loading rounds on the target. Thats not where most folks are.

If the bulk of your shooting will be FMJ's, I don't think you'll notice a difference between a 7 or 8 twist. If you're planning to shoot thin jacketed varmint bullets as well, the 8 might be kinder to those bullets...but bore finish is probably a bigger factor than twist rate in that equation.

Yes...everything was headed toward a 9 with the 62gr SS109 projectile, but it was found a 7 was needed for the M856 tracer in Arctic conditions.

The issue kinda solved itself

8:1 twist was what was available
I will let you know how it does

1 in 8" will be just fine.

My 1:8 Black Hole has never liked heavies. 73 ELD’s, 75 HPBT’s, 75 A-Maxes (cut the front out of the mag), none of them. Never tried any non Hornady offerings.

It did fairly well with Sierra TGK’s.

Lately, it’s just been fed 55SP’s and 53 V-Max’s. The 53 is pretty amazing in my rifle.

Might be worth mentioning that BHW uses polygonal rifling in their barrels, which could have something to do with its distaste for heavies.

Twist rate is a bit over hyped. I have made ARs with twists from 1-9" to 1-6.5". All barrels of very high quality shot extremely well and twist rate can't make up for lesser quality. For dedicated use of bullets from 70 grains and up, I'd probably go with a 1-8. But as of this writing my most accurate rifle firing 75 and 77 grain bullets has a 1-9" twist and does fine at all ranges. the old 1-12" and older 1-14" are too slow for very long bullets, but from 1-9 and faster you'll find little difference if all barrels are of high quality.

Remember the older Speer 70 grain semi-spitzers? I used a few thousand of them in an AR made in the 70s with a 1-12" and also a 22-250 with a 1-14 and they shot MOA in both rifles. Now that bullet is a semi-spitzer with a flat base to make it shorter then one of the long range bullets of today, but it's still not that short, AND it was designed to work in 1-12 and 1-14 twist rates. It did just fine.
This is not to say twist rate is unimportant. I am simply saying it's not AS important as bore quality. If you actually use bullet from 65 to 75 grains in a good 1-9" you'll see the same thing I see. It's just fine. So is 1-8 and 1-7

you cannot over stabilize a bullet, may get a bit of yaw with fast twists and light bullets slightly affecting accuracy, but they will settle down,, I have them twisted 7,8,9,10 and 12, best shooting one of the bunch is an 8 twist with 55, 60, 62, and 69 gr bulllets,, so is it twist or the individual barrel? with bullets below 75 gr an 8 twist quality barrel will be fine

Sounds like you got a chidty barrel. Most 1 in 8's shoot those bullet weights quite well. I've shot a lot of 73's, 75's, 77's in all of mine. NO problems whatsoever. I'd be looking at getting a better barrel.

All of my current uppers have barrels with 1/8 or 1/7 twist. They seem to like 69-77 grain bullets although that may be because the rounds I shoot with heavier bullets use higher quality bullets and are generally handloaded.

I use bulk 55 grain ammo (mostly Federal American Eagle bulk pack) in short range matches because I shoot a lot of it, it's cheap and at short range it's sufficiently accurate. But I don't generally get better than 1.5 MOA 5 shot groups from the bulk ammo, whereas I get sub MOA with 75 grain handloads. But maybe it's due more to quality than bullet weight.

I haven't had any reason to load some high quality light bullet loads and test them.

You probably won't be shooting 600 yards, most don't. The 8 will be just fine, as noted, assuming the barrel is good.

I'm a 1:9 or slower guy, as I ONLY shoot bulk 55gr fmj stuff.

Shoot bulk 55 gr. M193, as well as 55 gr. Barnes TSX hunting ammo, and limit shots to ~ 200 yards, carbine range.

1:9 twist 580-Series Mini-14 w/ aperture sights.






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