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  #1  
Old 05-29-2016, 10:18 PM
Capt. Methane Capt. Methane is offline
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So what is the truth about .223 and rifling twist rates?

Because I'm reading all this stuff by various "experts" about bullet weights and rifling twist rates and I'm wondering if a 1 in 7 barrel (like many of them seem to be these days) can be accurate with a 55 gr bullet...
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Old 05-29-2016, 10:24 PM
The Earl o Sammich The Earl o Sammich is offline
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Easy answer, from someone who's been shooting High Power Competition for the last 30 years;

... it depends

How fast are you pushing them?

How far you shooting them?

Are you talking 2 minute of angle?

Are you talking one hole, 1/2 minute of angle, pop a crow at two hundred yards?

Just shooting surplus or do you load your own?

What does accuracy mean to you?
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Old 05-29-2016, 10:31 PM
Gary in TX Gary in TX is offline
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I shoot more 55 grain stuff out of my 4 1/7's than I do heavier grain loads. All shoots really tight if I do my job. Sometimes I get tighter groups out of the 55 gr. stuff (depending on many variables). Much ado about nothing.

Then again I'm no expert, just a guy that likes to shoot.
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Old 05-29-2016, 11:05 PM
eby1911 eby1911 is offline
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Like Earl wrote, lot of variables come into play. But generally speaking, a 40 gr bullet will stabilize better in a 1/12 twist barrel and a 80 gr bullet will stabilize better with a 1/7 twist barrel. The heavier the bullet you want to shoot, the faster the rate of twist should be used to stabilize the bullet effectively. You could still shoot that 40 gr bullet out of a 1/7 twist barrel, it's just not as ideal. It will likely over-stabilize the 40 gr bullet and it will not be as accurate at long range. But a 40 gr bullet is not good choice for a long range bullet anyway. I have several ARs that are 1/8 twist. 69, 75 and 77 gr bullets are very accurate out of those barrels. My older ARs with 1/9 twist do better with the 55 gr bullets.

A a general rule:
1/12 twist for 40 gr bullets.
1/9 twist for 55 gr bullets.
1/7 twist for 77 gr bullets.
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Old 05-29-2016, 11:16 PM
Capt. Methane Capt. Methane is offline
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Seems to be a lot of "stuff" about this cartridge. It's not like some of the oldies I'm more familiar with-way more options to the rifles. Does anyone know the twist on the heirloom sproterized Enfield .30-06? Heck no, Grandpa used 168gr whatevers and XX.6 grains of some kind of powder and it just worked!

I'm new to the .223/5.56 but not to reloading so yes, I'll be reloading.

I'm more interested in accuracy than velocity as a goal-a fast noise never hurt anything! Coyotes are getting to be a bit of a problem locally so some predator control isn't out of the question-though a long shot around here would be 200 yds due to brush, trees and terrain with 100 yds more typical.

Minute of angle would be great for a start-heck, I don't have any glass on the AR (I'm going to fix that at some point) so at a hundred yards it's really all on me and I'll be the first to admit I don't shoot enough rifle and part of that is economics and the heavier bullets don't fit the bill for that-you see some pretty good bulk deals on 55 gr bullets from time to time.

On the other hand who wants 6000 bullets that won't shoot well in their rifle?
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  #6  
Old 05-29-2016, 11:51 PM
ClarkEMyers ClarkEMyers is offline
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Most assuredly a 55 grain bullet can show fine accuracy from a 1/7" twist. Better from a match chamber and chrome lining doesn't do much for air gauging a match barrel.

I am not yet persuaded that a good bullet can be over stabilized. I know that a just barely stabilized bullet shows a lower ballistic coefficient than the same bullet well and truly stabilized or over stabilized if you wish. I know that a less than perfect bullet does better when spun no faster than necessary. A slower spin does not stress the bullet as much. That is when the center of form and center of mass are off center spinning the bullet faster brings out defects. I also know that generalizing and speaking of or assuming all bullets of the same weight share the same characteristics is flat wrong. Hornady makes a lovely high ballistic coefficient bullet in the gap between 50 and 55 grain. The bullet has a boat tail and a large hollow filled with red plastic like material for a long sharp point and so the bullet is much much longer for purposes of exterior ballistics than a traditional flat base cup and core lead filled and lead pointed bullet. Although only 53 grain weight the Hornady bullet demands a faster twist than traditional twist. I see this as the wave of the future and although I have a nice Hart barreled Swift lost in the past with a 1/14 twist as once popular for home made cup and core bullets in traditional short range bench rest in the future I will be buying barrels with amply fast twists. I don't expect to suffer much from over stabilizing available bullets. I suspect that any inferior performance with the 1/7 twist is that most such barrels in common use are chrome lined and 5.56 chambered rather than match chambers in match rifles. Of course when used in a match rifle the hgh ballistic coefficient bullets will be used but afaik the same rifles do well at shorter ranges with 55 grain bullets.
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Old 05-30-2016, 05:43 AM
Chickenthief Chickenthief is offline
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How damaged bullets fly:

https://www.youtube.com/watch?v=C9Dylxy3zJc

Food for thought.
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  #8  
Old 05-30-2016, 07:41 AM
RickD1225 RickD1225 is offline
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Capt., here is a link to a good primer on .223/556 cartridges.

http://www.accurateshooter.com/cartridge-guides/223rem/
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Old 05-30-2016, 08:35 AM
fr3db3ar fr3db3ar is offline
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To answer the original question. My 55 vmax shoot moa at 200 out of my 16" 1 in 7 AR.

Sent from my SM-T817V using Tapatalk
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Old 05-30-2016, 10:58 AM
Capt. Methane Capt. Methane is offline
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Well, no wonder this cartridge raises so many questions-the heaviest bullets are nearly three times the mass of the lightest!

Those links are very interesting and helpful.

Thanks guys, it's been a big help.
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Old 05-30-2016, 11:46 AM
moxie moxie is offline
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In the military we went from 1:12 to 1:7 when we switched from the M193 55 gr. bullet, to the M855 62 gr. bullet as the standard. The 1:7 was deemed adequate for 55 gr. up through all the heavier bullets.
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Old 05-30-2016, 11:57 AM
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If you use a quality 55gn bullet, accuracy will be fine.

Bullet length drives how fast of a twist you need. Obviously a heavier bullet will be longer and faster twist means more RPMs.
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Old 05-30-2016, 12:06 PM
CPTKILLER CPTKILLER is offline
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I use both 55 grain and 62 grain with no issued with my Sig 556XI with a 1 in 7 barrel.
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Old 05-30-2016, 04:56 PM
Old Grumpy Old Grumpy is offline
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I've been told that "back in the day" when the 5.56 was being introduced most of the data was coming from military data. The M16 had a certain twist rate and it had been designed to shoot a specific weight bullet at a designated velocity. Then the shooting public started "tweeking" the .223 Remington. Different weight bullets were being produced along with different twist rates. I was told the new twist rates didn't work that great with some bullets.

The take into account the improvement in bullets. I know the quality of today's bullets are leaps and bounds ahead of bullets available in the 60s and 70s. Bottom line I've been told is today's light weight bullets are of high enough quality to acceptably stabilize out of a faster twist rate barrel.

I am also a newbie at reloading the .223 Remington so I may be way out in left field but this makes sense to me.

Grumpy
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Old 05-30-2016, 06:25 PM
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hal copple hal copple is offline
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My M&P splints the difference with a 1 in 9 twist. i usually shoot 62 grain bullets, and am content with my accuracy. Just remember to peruse the internet for the important differences between 223 and 5.56. I was hoping to pick up a bolt 223 gun to go with my AR, so I could just shoot the same loads in both. But that would mean having to load every round for the 223, giving less accuracy in a 5.56. So don't think I'll get the 223.
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Old 05-30-2016, 07:00 PM
cavelamb cavelamb is online now
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See if this helps?

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Old 05-30-2016, 08:33 PM
USMM guy USMM guy is offline
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Count me into the group.

That says the quality of the bullet will matter more in the set of circumstances that you are referring to. Particularly when consideration is given to the range you are looking at. I am thinking that you can take a 50 grain Nosler ballistic tip, or the equivalent from Hornady, or any of the other top tier makers for that matter. And for coyotes at less than 200 yards you should be good to go. As long as you can do your part.

Heavier bullets really come into their own at longer distances for a number of reasons. But fast light, well constructed bullets within reasonable range can be devastating. You may even want to try out some of the Barnes TSX bullets.
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Old 05-31-2016, 08:21 AM
WalterGC WalterGC is offline
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I've shot a bunch of 1/2" groups @100 yds, shooting 55gr bullets through 1/7 barrels.😉
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Old 05-31-2016, 08:22 AM
starcommtrey1 starcommtrey1 is offline
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Quote:
Originally Posted by eby1911 View Post
Like Earl wrote, lot of variables come into play. But generally speaking, a 40 gr bullet will stabilize better in a 1/12 twist barrel and a 80 gr bullet will stabilize better with a 1/7 twist barrel. The heavier the bullet you want to shoot, the faster the rate of twist should be used to stabilize the bullet effectively. You could still shoot that 40 gr bullet out of a 1/7 twist barrel, it's just not as ideal. It will likely over-stabilize the 40 gr bullet and it will not be as accurate at long range. But a 40 gr bullet is not good choice for a long range bullet anyway. I have several ARs that are 1/8 twist. 69, 75 and 77 gr bullets are very accurate out of those barrels. My older ARs with 1/9 twist do better with the 55 gr bullets.

A a general rule:
1/12 twist for 40 gr bullets.
1/9 twist for 55 gr bullets.
1/7 twist for 77 gr bullets.
Are you sure that is not backwards? Usually 1/12 twist is for larger grain bullets and smaller is for lower grain bullets.
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Old 05-31-2016, 08:34 AM
starcommtrey1 starcommtrey1 is offline
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Well never mind....5.56 are funny things.

However, I have come to learn each caliber has an optimum twist rate, 30 cal is 1:10, 223/5.56 is 1:7, 44 mag is like 1:15 or so. Length of bullet has a lot to do with twist rates as well.
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Old 05-31-2016, 08:49 AM
jmorris jmorris is offline
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I have ran many 55 gn bullets out of 1:7 twist barrels with no problems.

I did have some varmint bullets IIRC Speer, that were intended for the slower twist of bolt guns, that came apart with the 1:7 due to centrifugal force.
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Old 05-31-2016, 11:31 AM
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I was reading about the Army's new "green" bullet, which was chosen, apparently, without concern for ballistic performance.
In a 1:7 rifle, it's good for about 4MOA, while in a slower twist it will do 2MOA, so the Army has the bullet demonstrated by the AMU, which uses slower-twist (1:8?) barrels.
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  #23  
Old 05-31-2016, 05:00 PM
Capt. Methane Capt. Methane is offline
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Quote:
Originally Posted by starcommtrey1 View Post
...5.56 are funny things.
I was kind of thinking that too but the replies have helped disperse much of the fog around the issue.

Now I've got a mess of 55gr for practice-I don't need to push them fast for that, some 69gr Nosler BTHP's and I'll try some of the others. I never was much of an AR fan but the bug has kind of bitten me...even if the 55gr bullets don't give optimum performance from the rifle they will give me much needed practice!
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  #24  
Old 05-31-2016, 05:36 PM
Twoboxer Twoboxer is offline
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If a bullet spins too slowly for its length it will be or quickly become unstable. This effect is significant (duh).

The faster a bullet spins, the more its imperfections cause deviations from the expected trajectory. Spin drift also increases. Finally, the (small) vertical component of a crosswind induced by spin increases. Spin drift can be compensated for and the very small vertical effect of a crosswind can be ignored.

At some point for some bullets excessive spin rates can cause the jacket to come off the bullet.

Bottom line:

An ideal spin rate for a bullet keeps it stable without introducing/exacerbating the effects of yet faster spin rates. Spin rates significantly faster than necessary can cause unnecessary changes in trajectory (some calculable, some to be ignored). At some point, catastrophic separation may occur.

TLDR: In most cases a good 55gr bullet should survive 1-7 twist. As always, testing will determine whether your rifle likes shooting them enough to satisfy you.
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  #25  
Old 06-01-2016, 11:32 AM
nogoodnamesleft nogoodnamesleft is offline
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My 1:7 twist upper (Superior Barrel's 16" barrel) shoots 50 gn V-MAX just fine. Using a 7X scope, I can get less than 1 MOA for 5 shot groups and real close to 1 MOA for 10 shot groups.







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