AR-15 Twist Rate information.

DadSmith

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I noticed there is a lot of people asking about and some confusion about AR-15 5.56 and 223 twist rate. So thought I would post this as a guide.
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Hopefully this is helpful.
 

T-DOGG

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I shoot 55 grain out of 1:7 twist barrels frequently and have only experienced tumbling/keyholing once at 100 yards using a BCM and Wolf Gold. And that was a fluke for a few rounds with that ammo.


My 18" Noveske 1:7 averages 1.61" suppressed and 1.63"unsuppressed at 100 yards, with a best of 1.06".
My 16" BCM 1:7 averages 2.14" at 100 yards, with a best of 0.79".

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DadSmith

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1/12 is 55 grain, OR the US military was wrong for over 30 years
The M4 has been 1-7 from the beginning even the M16 went to 1-7. It's been 1-7 since the 1990's at least. My 1-8 will shoot some 55gr good but not all. It likes 75gr bullets the best. The only 62gr bullet it shoots accurate is Wolf Military Classic 62gr HP that I have found so far. It doesn't like M193 or M855. At least the federal version. 1-12 will shoot 55gr and down to 35gr. My buddy has a varmint rifle with that twist and he uses 35gr and 40gr a lot for that high velocity.
 

T-DOGG

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I think it worth noting that you could get decent results at 100 yards with a bullet that isn't properly stabilized that might not be indicative of what would happen at 300 or 500 yards. The bullet is losing energy throughout its flight.
Fair enough. I haven't tested anything 55gr past 100 yards. Might have to put that on my "to do" list.
 

DadSmith

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rob63

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Fair enough. I haven't tested anything 55gr past 100 yards. Might have to put that on my "to do" list.
FWIW, I don't think the issue would be shooting light bullets in faster twist barrels, but rather the other way around. I could be wrong, but I think the chart is showing the minimum twist necessary to stabilize the particular weight.

In any case, I do think you are correct that it would be worth adding to your to do list. I hope we see the results some day.

Edit: reading the article above, I think the chart might be geared towards best accuracy rather than minimum necessary.
 

T-DOGG

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FWIW, I don't think the issue would be shooting light bullets in faster twist barrels, but rather the other way around. I could be wrong, but I think the chart is showing the minimum twist necessary to stabilize the particular weight.

In any case, I do think you are correct that it would be worth adding to your to do list. I hope we see the results some day.

Edit: reading the article above, I think the chart might be geared towards best accuracy rather than minimum necessary.
I just added it to my list of stuff to "test and tune". I'll test Wolf Gold 55gr at 200 and 300 yards with the Noveske and BCM.
 

JeepHammer

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1/12 is 55 grain, OR the US military was wrong for over 30 years

YUP!
1:12 was the military standard for a little over 30 years.
I've had several of the current generation argue against what is stone cold fact.
(Don't argue with idiots, wastes your time and onlookers can't tell the difference)

Even some 1:14 out there, the (mostly) Air Force semi AR15's on the very front end of the Vietnam war.

Israeli military had some short barreled patrol rifles with 1:14.
Their standard bullet for a long time was 52 grain square base, and 1:14 worked quite well, square base giving more load bearing area than boat tails did.

I see quite a bit of debate about light weight bullets, which .222/.223 started out as a varmint round.

I guess the later generations (and the BoobTube 'Experts') don't know about the rifling cutting through and stripping off the jackets on 30/35/40 grain bullets...
Fast twist rates simply cut through and stripped the jackets off thin jacketed varmint bullets back when folks were still figuring out the high velocity, small diameter bullets.
I guess you had to be there since no one talks about it now...

How many remember the grandpa of the current .223/5.56 NATO rounds?
.218 Bee, .219 Zipper, ect.?
Or the father, .222?
Some of those had 1:16" twist and do quite well today even by modern standards.
 
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MrSmitty

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I loaded up some 77 gr boolets over some varget for my MSR...thought it was 1 in 7....wrong...it was 1 in 12....every shot a keyhole....changed to 55 gr, much better...My recent shoot at the Hide not withstanding.......
 

Hookeye

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Buds Mini 14 ranch ( earliest model ) would rip apart Hornady 55gr SX. Dunno what twist rate was. Said bore wasnt the most smooth.

Got a .219 D Wasp and dunno what the twist on it is. 50gr Nosler BT do sub half inch at 100. Supposedly nips at 22-250 heels....I dont have a chrono.

Not interested either. Its hot enough and accuracy is there. No need to try to squeeze out more of either.

Do think 55s in an AR about perfect yote machine. Tried across 3 different ones.....the V max or Winchester Supreme stuff both shot well.

Exits kinda large but can be sewed up LOL
 

Tyler-The-Piker

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Buds Mini 14 ranch ( earliest model ) would rip apart Hornady 55gr SX. Dunno what twist rate was. Said bore wasnt the most smooth.

Got a .219 D Wasp and dunno what the twist on it is. 50gr Nosler BT do sub half inch at 100. Supposedly nips at 22-250 heels....I dont have a chrono.

Not interested either. Its hot enough and accuracy is there. No need to try to squeeze out more of either.

Do think 55s in an AR about perfect yote machine. Tried across 3 different ones.....the V max or Winchester Supreme stuff both shot well.

Exits kinda large but can be sewed up LOL
Any experience with this?
I've had a bunch for a few years...(bought it mainly for 2-legged critters/HD...ive never gotten a coyote)

 

DadSmith

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Now the solid copper 55gr rds you can probably shoot in a 1-7 because they are definitely longer than copper and lead 55gr. I think it is the length of the bullet that determines what twist will give it the best accuracy. Not an expert on this subject so I'm open for discussion and learning.

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0.868 length 55gr Lehigh

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Hornady 55gr FMJBT 0.735 length

Hornady 62gr FMJBT is 0.813 length.
 
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Bill2905

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I recalled reading this in my Speer reloading manual a long time ago so I looked it up again and here is what it says. Just a concise summary of what has already been commented above.

Original military and commercial rifles had a 1-in-14 rifling twist, later changed to 1-in-12 inches for better long range stability with the 55 grain service bullet. However, when the military adopted a heavier, 62 grain service round, military rifles were fitted with 1-in-7 twist barrels to handle the new bullet.
 

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