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Old 10-20-2019, 11:23 PM
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Fast twist rimfire precision?



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In AR conversion threads, the twist is often pointed to as a cause of imprecision. I'm not convinced it has a greater effect than one of or the collection of other causes.


Has anyone tried a fast twist barrel in an otherwise normal bolt action or dedicated AR rig, or have a link to such a test?

Last edited by H-R-B; 10-22-2019 at 04:02 AM.
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  #2  
Old 10-21-2019, 02:52 AM
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It all depends on the bullet you plan to shoot. I do not own an AR, but my bolt action .223 I had a custom 1-14 twist barrel put on it, which most say I am crazy, but with 55 grain bullets, it will shoot tiny wadded hole groups. Everyone else tells me that a 1-14 twist barrel will not stabilize a 55 grain bullet. I have proof to the contrary.

Now, there are twist rates that are RECOMMENDED for certain bullet weights and or profiles. It is not a fixed thing. It is just a starting point to work from. If you might shoot different bullet weights, then you want to find a twist rate in the middle somewhere that will handle both.

From what I know, most AR's are a 1-8 twist or so.... so how much faster were you thinking?

Last edited by Gizzy; 10-21-2019 at 02:55 AM.
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Old 10-21-2019, 08:33 AM
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Back in the day, most of the 22 centerfires were 1 in 14. 50-55 grain bullets were the norm and accuracy was great. Then the military decided the .223 was a "long range" rifle and needed heavier bullets, so, now we have 1-7, 1-8 twist barrels. They do not shoot light bullets well.
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Old 10-21-2019, 09:25 AM
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Gizzy, you did the right thing 1-14 twist 52g to 60g for that twist, all my rifles back in the 70s in 22 caliber had a 1-14 twist my Savage 112V J action 22-250, my 40XBBR 222 and other 1-14 twist, 53g and 55g gave me the tightest groups.
My brother just gave me Rem. 700 SPS in 223 it has 1-12 twist working on loads for it now, my luck 100 & 200 range was closed down for remodeling that could be months, still can learn much at 50yds, Berger 55g HP 24.5g Wim. 748, 5 rounds under .100 looks like one ragged hole. All so liked 45 yr old Rem. 52g Match 24.8g Wim. 748.
l have a couple of 100 rounds of 224 to play with.
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Old 10-21-2019, 10:33 AM
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Stabilization isnt just a bullet weight thing for a given twist though we tend to 'talk in weights' because it is convenient. It is a length thing but the shape; ie, where it carries the weight/shape of the ojive and velocity; ie, a faster velo can stabilize a marginal for length projectile 'sometimes' will work. Typically heavier, which is longer, bullets require more twist to stabilize. Distance intended to shoot is an issue also since a bullet that is stabile and groups well at x distance but falls apart at y may not be what you want.
The rule of thumb is,"when choosing a barrel twist for a given weight/length err to the faster twist because a marginal twist cannot be depended upon to work and rarely can be overcome with more velo". Why not, because cartridges are usually loaded pretty well peak for velo and pressures so going overpressure isnt an option.
Ive had some chance to experiment with how heavy/long bullets I can get to group well in given barrels and found that I can get good groups with some lighter/shorter bullets in a barrel for heavier/longer than the other way around; ie, 'over-stabilization' is, within reason, a myth. (for my purposes, ymmv) Imo, the primary reason the lighter/shorter in the fast twist may not group well At Distance is not the weight/length but the poor ballistic coefficient. Nobody I know uses light/short bullets as match bullets if they have an option of using longer/heavier.
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Old 10-21-2019, 02:07 PM
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In my experience with ar's in .223 cal, a twist of 1 to 7 or 8 or 9 , is beneficial for the heavier bullets and longer length. In a .22lr those twists have given mediocre accuracy and caused severe leading in the barrel starting in front of the chamber. One generally does better with a 1 to 12 or 14 twist in a .22lr.
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Old 10-21-2019, 02:13 PM
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1 in 12 or 1 in 14?

Are 22lr firearms not almost universally 1 in 16 twist?

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Old 10-21-2019, 04:39 PM
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Yep
Though back about 100yrs ago some few 22LR match shooters were using a 1:14 and believed they had an edge on the rest o' the boys. They were top-notch shooters anyway and the reference I stumbled across was as regards off-hand matches. Impossible to know if it made them win/place more than usual.

Last edited by gcrank1; 10-21-2019 at 04:43 PM.
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Old 10-21-2019, 11:17 PM
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Gcrank1's explanation about bullet stability for a given twist rate is exactly right....it is the length, plus the shape of the bullet, both front and rear, because the profile also affects the bullet's center of gravity and stability, as well as weight. Some shorter, blunter, but heavier bullets for caliber may be more stable than another somewhat lighter, yet longer and more streamlined design, when fired in the same twist barrel. Like Lefty 222 notes, I owned a '70's era Savage 110 series .223 varmint rifle with a 1-14" factory twist heavy barrel. Though theoretically not stable, it shot everything up to a 65 grain bullet extremely well....however 69 grain Sierra Match Kings, would already be unbalanced and gyrating wildly by 50 yards. Conversely, a newer 1-9", short action Model 12, shoots 40 and 45 grain bullets very accurately, despite being "over" stabilized....and will shoot certain 75 grain bullets well, as long as good velocity is maintained. I think the quality and strength of the bullet jacket has more to do with the light bullet's performance....some very light, ultra thin, explosive, conventional hollow point varmint designs will become erratic or even come apart through too much RPM, even at velocities capable from a .223. Polymer tipped bullets of the same weight, with a heavier jacket, and higher B.C. don't exhibit this, in my experience. On a side note, I also like Win. 748 powder for .223 reloading.
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Old 10-21-2019, 11:56 PM
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Quote:
Originally Posted by wkd View Post
They do not shoot light bullets well.

Oh. I wasn't aware - https://youtu.be/5AEPwOa623I?t=1154



To others, what I'm looking for is a test of a normal precision rimfire rig, but with a fast twist of 1:7-1:9 to isolate the twist as the difference. Having another one in 1:16, but with an elongated freebore or .219/.224" bore would be great, but twist is the point most folk tend to hang onto.

This isn't looking for a performance advantage, but clarifying what causes imprecision in converted ARs.

My doubt stems from a little experience with cast boolits in a well worn .30-06. A 165gr cast boolit at 1600fps would ideally prefer something like 1:15, but they were quite decent through the 1:11. Besides cast vs swaged and gaschecked vs heeled, I don't see much difference in comparison to rimfire.
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Old 10-22-2019, 01:27 AM
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I read the words AR and automatically went into centerfire mode. Now, I will say that the most accurate factory rimfire in my opinion is the Anschutz, which has a 1-16 1/8" twist. Slower, not faster. Something to think about, since they are built to shoot a match bullet of 40 grains, and most other ammo have lighter weigh bullets, other than the 60 grain Aguilla.

What are the converted AR's in .22lr you are talking about? What is it you think makes them inaccurate?
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Old 10-22-2019, 04:01 AM
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Quote:
Originally Posted by Gizzy View Post
What are the converted AR's in .22lr you are talking about? What is it you think makes them inaccurate?

Any of them.


- Adapter neck inside diameter.
- Adapter neck outside diameter fit inside the centerfire neck diameter. Concentricity of the adapter bore.
- Jump, bullet hardness, velocity, relevant harmonics.

Last edited by H-R-B; 10-22-2019 at 04:10 AM.
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Old 10-22-2019, 08:27 AM
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ARs have a bore diameter of 0.219 Grove/0.224grove while 22lr have a bore of 0.222 grove/0.217 bore diameter IIRC. This is why people see the poor accuracy they do from AR conversion units.
Twist wont make a lot of difference if the bullet is skipping down the barrel. That said the general belief amount bench shooters is to use the slowest twist that fully stabilizes your bullet. If Im not mistaken the SAAMI twist for the 223 remains 1/12 while the 5.56 NATO is based on CIP Standard and is set at 1/7. These are two different cartridges by the way, although the 223 will safely chamber and fire in a 5.56 chamber.
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Old 10-22-2019, 10:09 AM
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Quote:
Originally Posted by H-R-B View Post
Has anyone tried a fast twist barrel in an otherwise normal bolt action or dedicated AR rig, or have a link to such a test?
The author of the 8th post in the following thread used a 10/22 and tested 60gr, 40gr and 38gr.

http://forum.accurateshooter.com/thr...10-22.3749124/
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Old 10-22-2019, 02:01 PM
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Quote:
Originally Posted by zukiphile View Post
The author of the 8th post in the following thread used a 10/22 and tested 60gr, 40gr and 38gr.

http://forum.accurateshooter.com/thr...10-22.3749124/

Thank you.

With normal fodder, 0.8" at 50yds is better than the 0.8" at 50ft I've come to expect or sometimes hope for from a conversion. Sample of one shows twist to not matter as much.
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