AR-15 barrel twist rate


PDA






kawtech87
April 12, 2011, 10:30 PM
Hello, im new to THR but ive read alot of post as a guest and always found them helpfull. So now i decided to join so i can ask pointed questions and learn more about specifics. Like this one, ive shot several ARs and have a Ruger SR-556. All have had a 1/9 twist barrel. I was wondering is there really any difference accuracy wise between a 1/7, 1/8, and 1/9 twist rate? I normally use 55gr ammo and hardly ever shoot over 200 yards, so would buying an upper that has a barrel with a different twist really help my groups? any info would be greatly appreciated. Thanks.

If you enjoyed reading about "AR-15 barrel twist rate" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!
mc223
April 12, 2011, 10:36 PM
Somebody start a fresh pot-o-coffee and maybe popcorn. :what:


http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi


Sorry, just being human with a bit of humor.





Oh-Yeah, Welcome to the Forum

kawtech87
April 12, 2011, 10:44 PM
Hello, im new to THR but ive read alot of post as a guest and always found them helpfull. So now i decided to join so i can ask pointed questions and learn more about specifics. Like this one, ive shot several ARs and have a Ruger SR-556. All have had a 1/9 twist barrel. I was wondering is there really any difference accuracy wise between a 1/7, 1/8, and 1/9 twist rate? I normally use 55gr ammo and hardly ever shoot over 200 yards, so would buying an upper that has a barrel with a different twist really help my groups? any info would be greatly appreciated. Thanks.

kawtech87
April 12, 2011, 11:01 PM
Thanks mc223. But honestly that stability calculator just made me confused. Im not a reloader and dont know alot of the indepth info it asks for. Im a recreational shooter and have been wanting to try my hand at some 3 gun matches. I guess what i shouldve asked is if anyone has experinance with different twist rates in match settings, and what shoots match ammo the best? i know i dont want to use my Ruger (atleast not the upper) its to heavy to run around with.

68wj
April 12, 2011, 11:07 PM
For 55gr, there will be no improvement in accuracy. If you start loading longer, heavier bullets, the faster twist will start to come into play. You're fine.

kawtech87
April 12, 2011, 11:28 PM
Ok. Thanks 68wj, thats exactly what i wanted to know.

Lovesbeer99
April 12, 2011, 11:30 PM
Twist rate won't make your gun more accurate. It will only change the weight of the bullet you use. (I'll generalize) Most Varmint shooter like light 40gr bullets so they choose twist rates like 1x12. Long range target shooters like heavy bullets like 80gr so they use 1x7. Most like to use something in between like a 1x9 which can shoot many bullets fairly well. I had a 1x9 and I shot 52gr mostly but also 55's and 69's.

You must find the best round for your specific barrel. For 1x9 try 52, 55, 69, and see which ones works best.

mc223
April 12, 2011, 11:41 PM
Accuracy is not dependent on twist. There are really no hard and fast rules other than the slowest twist that will adequately spin stabilize the desired projectile.
Since you don't reload you are at the mercy of the factory type loadings and extensive testing can get expensive. However I think that unless you just have a ton of cash laying around that you can use for an upper. Find Ammo that works as near to what you want with what you have. I have a couple 1 in 9 barrels that shoot very well from 50g to 75g bullets. I also have a 1 in 8 that is not so hot with 55g and less and yet another 1 in 8 that just loves the little 52s. Your results will vary and sometimes from ammo batch to the next

If you have your heart set on a new upper, I would recommend you call John Holliger at White Oak Armament and explane what you want to do and your end use. You would be very happy with one of Johns uppers and his recommended ammo.

My feeling is that unless you are shooting 80g bullets exclusively there is no need for the 1 in 7.

If you only want to shoot the cheap 55s, what you have is fine. Either upgrade Optics, ammo, or work on technique to improve groupings.

kawtech87
April 12, 2011, 11:49 PM
Ok so heavy bullets need a faster twist and lighter ones a slower twist. But accuracy will be the same for either as long as its the appropriate grain for the twist. I get it. I would love to play around with more types of ammo and different grian bullets, but my ammo budget keeps me limited to whatever the gun shop has on sale in bulk, normally winchester 55gr. I can normally keep between a 2 and 3 inch group with it. Ill start playing with it as soon as the weather figures out its spring and starts to warm up. Thanks alot for the info.

mc223
April 13, 2011, 12:10 AM
It not actually the weight of the bullet it is the length of the bullet. Heavier bullets tend to be longer. Longer bullets need faster twist to stabalize in flight.

A 2 to 3 in group is a dead deer where I come from. I shake that much when it gets cold.

helotaxi
April 13, 2011, 12:22 AM
Lighter bullets don't "need" a slower twist but they can be shot with a slower twist. Twist rate only determines the longest bullet that the barrel can stabilize. You might lose some accuracy shooting Winchester 55gn FMJs from a fast twist barrel, but only because the fast twist exacerbates the effect of the Winchester bullets being horribly balanced. If you look at the base of the Win projectiles, they are very inconsistent. Spinning that faster than necessary causes the bullet to wobble excessively.

Bottom line, if you're shooting ammo that 1) is easily available and 2) loads from the magazine, a 1:9 twist is fine.

kawtech87
April 13, 2011, 12:23 AM
mc223. Thats true here too but i cant hunt with my AR here. Indiana only allows rifles in pistol calibers. Nothing high powered. Thats what my Marlin 1894 in 44mag is for. By the way, no i dont have a ton of cash right now. Im a motorcycle tech by trade and winter in indiana SUCKS for me! I only have about six months to make all my money for the year then i spend the winter blowing it on new toys and food. The upper ive been looking at is an RRA elite comp for about $800.00 and my favorite toy store has it on the shelf. whats the base price on one that mr. Holliger builds and whats the approximate wait time?

BushyGuy
April 13, 2011, 12:28 AM
1/7 burns up the barrel faster then a 1/9 twist rate, 1/8 is in between.

i am happy with 1/9 twist rate but i would like a 1/8 not a 1/7 thats too fast!

mc223
April 13, 2011, 12:34 AM
Holliger uppers will probly be about 6 weeks. Heres a link prices are on the complete uppers page.


http://www.whiteoakarmament.com/


There are other variants available also. Like camo and flutes etc.

kawtech87
April 13, 2011, 12:37 AM
So a faster twist can cause premature barrel wear? Ive never heard that. Is that just non chrome lined barrels or does it happen on chrome barrels too?

kawtech87
April 13, 2011, 12:44 AM
Thanks for the lead mc223 he has good prices and looks like a quaility product. i will definately give him a call.

mc223
April 13, 2011, 12:45 AM
Ive heard it but never personally seen it. Kindof sounds likely with the bullet seeing a lot of spin acceleration in a very short distance.


Holligers products are what the winners use. Each is built to your spec. And yeah the pricing is good.
He uses Kreiger barrels on the high side and Wilson(not Wilson Combat) barrels to stay on the cheaper side. All of the Wilson's that I have are very good shooters within the preferred ammo for each.

john5036
April 13, 2011, 01:54 AM
Try these links, they link to gunblast.com where this gentleman did a nice little video for YouTube, and then did a write up concerning the bullet weights/performance up to 77gr.

Gunblast.com YouTube (http://youtu.be/O4nTJvvLF3I)

Review at Gunblast.com (http://www.gunblast.com/Ruger-SR556.htm)

mc223
April 13, 2011, 02:23 AM
With all due respect to Mr. Quinn there just doesn't seem to be very many products that he don't like. I have all but abandoned Gunblast as a point of reference because of what seems to be very biased revues.

From Gunblast
Winchester USA 55 FMJ velocity 2858 group 1.75


So kawtech87 if you adjust your grip and hold your mouth just right you should get a inch and three quarter group. Of course this could be really crappy and was fired at 50yds which would make your groups at 100 bout right.

Another point is the piston op system does tend to put some accuracy robbing stress on the barrel.

madcratebuilder
April 13, 2011, 08:20 AM
http://i32.photobucket.com/albums/d37/madcratebuilder/50923489.jpg

Robert
April 13, 2011, 10:32 AM
Madcrate hit the nail on the head. Great chart!

Burning up an AR barrel will take somewhere in the neighborhood of 10,000 plus rounds, maybe more on a chrome lined barrel. I run an unlined 1:7 barrel and have no issues. I like 1:7 as it gives me the best selection of bullets that it can easily stabilize. It will not shoot the very light varmint bullets that well, but I'd rather use 55 grain bullets anyway, or heavier.

NAVY SEABEE 303
April 13, 2011, 01:36 PM
How will barrel length effect accuracy? For example on my AR I have a long (26") barrel with a 1in9 twist. I haven't tried to take her out very far yet all I do know is it makes sub moa.

SpeedAKL
April 13, 2011, 02:53 PM
Keep in mind that it isn't just precision shooters who tend to favor 1:7 twist. If you plan on using your AR for defensive purposes, some of the best defensive ammo uses 70+ grain bullets.

helotaxi
April 13, 2011, 03:50 PM
1/7 burns up the barrel faster then a 1/9 twist rate, 1/8 is in between.

i am happy with 1/9 twist rate but i would like a 1/8 not a 1/7 thats too fast!

So a copper jacket over a lead bullet will wear a hardened steel barrel...that's a good one. If accelerated too hard in a super fast twist barrel (which 1:7 really isn't) the normal result is the bullet skipping across the rifling, getting some of the jacket shaved off in the process, before it starts tracking. This has essentially zero effect on barrel wear.

It is a myth that faster twist barrels don't shoot lighter bullets well. Yes bullet wobble is accentuated by a faster twist, but a bullet suffering from poor balance isn't exactly the gilt edge of accuracy to begin with. You might be talking the difference between a 3MOA round and a 3.5MOA round when going from a 1:9 to a 1:7. With well made bullets the difference is non-existent.

The only other issue worthy of consideration is that of bullet breakup. This is a factor of bullet design and construction, not bullet weight. There have been some very lightly constructed bullets produced intended for varmint shooting varmints with lower velocity cartridges (22 Hornet, .221 Fireball, etc...). Some of these bullets have a propensity to essentially disintegrate if pushed too fast or spun too fast. These bullets are usually easy to pick out in a loading manual either becuase they are specifically highlighted in the text or the load velocities listed are slower than the loads for heavier bullets.

The only other issue that even exists is that of a bullet not tracking its flight arc with its spin axis because of a high rate of spin. This has been shown to be less than a degree of variation at normal trajectories and will have no effect on accuracy over normal ranges (out to 1000yds).

helotaxi
April 13, 2011, 03:57 PM
How will barrel length effect accuracy? For example on my AR I have a long (26") barrel with a 1in9 twist. I haven't tried to take her out very far yet all I do know is it makes sub moa.
Once again, no effect on accuracy. With issue rifles (no optics) the M16 is easier to shoot well than the M4 sized weapon becuase of an increase in sight radius and the increase in available aiming precision that allows. Add optics to the equation and they are equals.

What the extra barrel length does give you in an increase in velocity and a corresponding increase in max lethal range. With most ammo the difference between a 16" and 20" barrel is about 200fps. Beyond 20" the gain per inch is less because of the limited powder capacity of the .223/5.56 case.

kawtech87
April 13, 2011, 09:44 PM
Thanks you guys for all your help. You've answered my question and then some. I think im gonna take mc223's advice and on my next day off give mr. Holliger a call and see what he has to say and what the out the door price is on a custom upper with a 1/7 twist. That way i can run heavier loads if i want to. I knew i joined this forum for a reason, and you guys are that reason. people who know what they are talking about and willing to share and listen. Thanks again

Zerodefect
April 13, 2011, 10:24 PM
I run 1/7 in carbines and 1/8 in SPR's. (.556 55-77gn)

Waywatcher
April 13, 2011, 10:26 PM
Good plan!

Enjoy!

mc223
April 13, 2011, 11:49 PM
Thanks kawtech87.


What do you think of that 600 Kaw in the Gator?

Lakedaemonian
April 14, 2011, 12:14 AM
like Einstien's theory on time being relative. accuracy is also relative. accuracy is realtive to twist rate -vs- bullet grain. for instance, some people will tell you that a 1/7 twist will handle a 62 grain round very efficiently. since your twist rate is 1/9 i would say a 55 grain bullet will be most efficient to your selected firearm.

suzukisam
April 14, 2011, 12:26 AM
holliger makes his 1:7 sdm barrel in a 16" instead of a 20" custom for darrel at D9firearms.com.. mine is insane, and I would very much recomend them.. darrel gets some great prices from john also, since he buys big lots.. here is mine.http://i243.photobucket.com/albums/ff98/suzukisam967m/ar/SAM_0010.jpg

benzy2
April 14, 2011, 12:32 PM
Also realize that the longer the barrel, the slower the twist needed, if you move to a powder that is more efficient in longer barrels. If you can push a bullet faster you need less twist to get the bullet to stabilize. A short barrel, or really a barrel that produces less velocity, needs more spin.

helotaxi
April 14, 2011, 12:53 PM
if you move to a powder that is more efficient in longer barrels.

All powders are more efficient in a longer barrel. You can't simply go with a slower powder for a longer barrel and faster for short. I doesn't work that way. Every cartridge and bullet combination have an optimal powder burn rate that is completely independent of barrel length.

If you can push a bullet faster you need less twist to get the bullet to stabilize. A short barrel, or really a barrel that produces less velocity, needs more spin.
The only time that this works is when the bullet is on the ragged edge of stability. Velocity is one of the destabilizing forces trying to upset the bullet. Adding velocity adds RPM to the bullet, but also increases the required RPM (though to a slightly lesser extent). If the bullet is unstable in a given twist and velocity, adding velocity within the capability of the same cartridge isn't going to be enough to make a difference in stability. To really make up for a slow twist with velocity, you're going to have to up velocity on the order of the difference between a .22 Hornet and a .220 Swift.

Bottom line, if you want to reliably shoot heavy bullets, you need a faster twist barrel.

benzy2
April 14, 2011, 01:04 PM
All powders are more efficient in a longer barrel. You can't simply go with a slower powder for a longer barrel and faster for short. I doesn't work that way. Every cartridge and bullet combination have an optimal powder burn rate that is completely independent of barrel length. Not a story I believe. Many powders will not fully ignite in certain barrel lengths. If you run quickload you can see how much of a given powder has burnt with any given cartridge in a given barrel length. There are powders are more suited to longer barrels that allow proper time to burn. Sure, you aren't going to toss Sporting Clays in an SBR and H50BMG in a 26" upper, but within the acceptable powders for a given round, some are more suited for long barrels and others more suited for short.

helotaxi
April 14, 2011, 02:36 PM
Whether or not the powder completely burns in a given barrel length is irrelevant to efficiency. Look at the difference in burn percentage in Quickload if you want, but a better indicator is to look what powder gives you the best velocity. You will find that regardless of burn percentage, the same powder gives the best velocity in both a long or short barrel.

You'll also find that powders that burn completely in a short barrel are often lacking in the velocity department because they are poorly suited to the cartridge.

Whether or not you believe it has no bearing on its veracity.

kawtech87
April 14, 2011, 10:21 PM
mc223, John Deere has used Kawasaki engine in all thier lawn and garden equipment for years. Mostly because they cant build a decent small engine to save thier life. Kawasakis are some of the best out there. Thats why everyone uses thier stuff or copies it...ie the "gator".

kawtech87
April 14, 2011, 10:27 PM
i was cheaking out mr. holliger's website earlier and found a barrel i think i would like him to use on my upper. His SDM (squad designated marksman) barrel. Anyone have one? Its 20 inches long and comes with a 1/7 or a 1/8 twist. Any thoughts or opinions?

mshootnit
April 14, 2011, 10:30 PM
1/9 is best for the platform.

kawtech87
April 14, 2011, 10:32 PM
i guess i should have checked out all the post before asking those questions. Sorry suzukisam, SWEET rifle!

suzukisam
April 14, 2011, 11:07 PM
kawtech- you can't get the sdm in a 16" from holliger..I don't think, at least you couldn't.. but if your interested d9Firearms.com has them.. darrel is a great guy.. you can call him and ask him any questions, he has several variations too..

kawtech87
April 14, 2011, 11:32 PM
Thanks for the info sam. Ill look into it. What kind of lower do you have?

suzukisam
April 14, 2011, 11:49 PM
that particular gun is a RRA.

it is equiped with:

RRA two stage trigger
RRA winter trigger guard
YHM FF tube
badger tac latch
WOA 16"sdm
ergo grip
levang linear comp
Leupold mk AR

but honestly I've used many different lowers.. I have used YHM, RRA, sharpes, dpms, cmmg... all with great results

kawtech87
April 15, 2011, 12:17 AM
Nice, ive been looking at an RRA elite comp upper my usual haunt has on the shelf (that is if it hasnt sold yet). Any experiance with them?

suzukisam
April 15, 2011, 12:40 AM
No I haven't.. I tell you what, I have gotten to where I don't even look at "factory" stuff. I built that rifle for about 1200.00 bucks, I don't think you can get the rifle I have off the shelf for anywhere near that.. I build them just exactly the way I like them, actually I've gotten lazy and I let Darrel make them for me... I usually have a tab running on some new project.. My .02 is build what you want, and don't look back...

Even the colt "perfection" doesn't do anything for me, I like what I've built better...

If you enjoyed reading about "AR-15 barrel twist rate" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!