AR15.Com Archives
 1/7 or 1/9 twist?
Brandon82  [Member]
1/17/2012 11:01:37 PM
Which do you prefer and why? Thanks in advance.
jncryer  [Member]
1/17/2012 11:05:26 PM
1/7 is for the heavier grain bullets. I typically dont shoot anything over 65grn, so I dont need a 1/7. I'm fine with the 1/9 in my Stag, but I like the idea of a 1/8, like on PWS setups, so that I can can have the ability to shoot 70 grn if I choose, while still allowing more reliable use of lower grns, as well.
strm_trpr  [Member]
1/17/2012 11:25:21 PM
1/7 is preferred, it does better with 65+ grain ammo and t will be just as good with 55 grain, I have seen rumors that it can cause the jacketing to come off of really light varmint loads 40 grain and lighter, but I have no first hand experience with this. plus why use less than 55 grain unless you are doing target shooting.
Aggie1188  [Member]
1/17/2012 11:27:03 PM
It depends on what the rifles use is. 1/7 is great all around as you can use it for home defense with the larger bullets to stop those bastards. 1/9 is nice for the range cause you can use cheaper/lighter ammo to punch paper. IMO
dcs12345  [Team Member]
1/17/2012 11:44:48 PM
Originally Posted By Aggie1188:
It depends on what the rifles use is. 1/7 is great all around as you can use it for home defense with the larger bullets to stop those bastards. 1/9 is nice for the range cause you can use cheaper/lighter ammo to punch paper. IMO


My 1/7 shoot just as well as my old 1/9 did with 55 grain surplus and wolf.
AR18  [Member]
1/17/2012 11:59:35 PM
Too me both are good. It is better than 1/12 or 1/14.
AR-180  [Team Member]
1/18/2012 12:02:48 AM
One in seven for sure. The faster twist will stabilize 77s. That bullet shoots great. Plus, the twist will still stabilize the 52, 53, and 55s.
B44T  [Member]
1/18/2012 12:56:21 AM
I went 1-9 as my 1-7 twist guns just flat tore up the thin jackets of my varmint bullets. Its shoots 55-62 gr. stuff well but shoots 69 gr stuff the best.
I also get better accuracy with my M261 .22 Rim Fire adapter.

Supposedly 77 gr. bullets will shoot well in some 1-9 twist barrels, preferably longer ones, but I have not tried it in my 16" gun.
My buddy shoots them well in his 20" 1-9 twist A2. He also has a 1-8 NM rifle that shoots those 80-something gr. bullets scary accurate at 600 Yd
They are too long to fit in the magazine and must be single loaded through the E-port.

ETA

FWIW my 1-12 twist SP1 shot 63 gr. varmint bullets acceptably well, their center of gravity is biased towards the ogive for best stability and accuracy.
M855 has a center of balance biased towards the heel of the bullet to promote instability upset upon entering denser mediums.
1-12 will not stabilize M855 worth a damn.
ru4freedom  [Member]
1/18/2012 1:09:03 AM
I used to prefer 1:9 ....., but now I'm sold on the 1:7

Most of my AR trigger time is punching paper to keep my chops up for taking yodel dogs at distance...., the further the better!! Loves it!!

The most accurate & lethal load I've come up with by far for my 5.56 & .223 AR's is a 63 gr. Sierra SP over 26.3 grains of Varget. COL @ 2.26"
I've been shooting this load for many years now in both of my 16" HBAR's w/1:9"...., groups are usually right at 1/2 MOA @ 100yds. with an occasional 1/4" group.

A few months ago, I got one of my 14.5" Colt HBAR 1:7 barrels back for getting a 51T BO mount perm. attached (We can finally use our Silencers is WA. now!)
Just out of curiosity I put my MK4 4.5-14 on it & much to my surprise, with my pet load this thing consistently shoots 1/4 MOA @ 100 yds!! The 55's & M855's Penetrators I shoot are factory loads & I don't get as tight of groups but they also consistently shoot tighter groups through my 1:7 I thought this might be a fluke, so I tried out my 14.5" 1:7 M4 profile barrel & while not quite as dramatic as the HBAR the M4 Profile 1:7 out shot my 1:9's for accuracy as well! I'm thinking it has to be the twist..., both of my 1:7 barrels are surplus Colt USGI chrome lined & I wouldn't think they would normally be conducive to that kind of accuracy!

I have no experience with thin jacketed varmint bullets through a 1:7...., but I can see how a 1:7 could...., & probably would frag 'em!!

I'm a "Flip-flopper" .., I used to use my 1:9's for dedicated optic rigs for accuracy shooting & the 1:7's for just blasting away with my Eotech & iron sights.
Now my 1:7's are carrying my optics for surgical work & my 1:9's are the Iron sight blasters!!!

Funny how influential some of these threads can be..., I had been so convinced from everything I had read over the years that 1:9 was the "best all around" that I had totally discounted my 1:7's..., using them for plinkers & never even testing them for accuracy......., go figure??

Of course now with my new revelation (late bloomer I guess)..., I'm jones'in to see what 1:7.5" and 1:8" twist barrels will do!!

What a vicious cycle this "Black Rifle Disease" has become!! Thank God there's no known cure!!

My hunger for accuracy can only be satisfied one ragged little at a time!!

JCunningham  [Team Member]
1/18/2012 2:20:59 AM
1/7 works with everything from 55-80g
FAB-10_Guy  [Member]
1/18/2012 3:16:19 AM
Originally Posted By JCunningham:
1/7 works with everything from 55-80g


I prefer 1:7. The only reason I keep the old BM 16" 1:9 around is for converting it to 22lr with my M261 conversion. However, I do shoot the 60gr Aguilla SSS through my 1:7's and they seem to do fine with that. They also do OK with the 40gr Federals at close range, but not the most accurate. Good for plinking though. I don't shoot 40gr 223 much anymore, so really don't need the 1:9 twist.
ColdBlood  [Member]
1/18/2012 4:55:51 AM
Only reason to go 1/9 is if you're shooting varmint loads well under 55 grain. Generally speaking, though, any ammo you find lighter than 55 grain isn't necessarily gonna be cheap. For general purpose (defense/plinking), I think 1/7 is where it's at...you can find 55 grain dirt cheap, and you can shoot 77-80 grain stuff too.

That said, I had a 20" 1/9 barrel that loved 75 grain ammo out to 100 yards, but that's as far as I ever shot with it. I don't know how well it would actually do for any distance shooting....from what I hear, some will stabilize them, some won't. I imagine length would be a factor there too....shorter 1/9's might not do so well.
aaholland  [Member]
1/18/2012 6:15:37 AM
1/7
d90king  [Member]
1/18/2012 6:57:45 AM
1/7. It allows me to shoot the widest variety of ammo.
FMJ  [Team Member]
1/18/2012 7:08:02 AM
1/7

45gr to 100gr

whats not to like
tlwest1986  [Member]
1/18/2012 9:35:05 AM
Originally Posted By AR-180:
One in seven for sure. The faster twist will stabilize 77s. That bullet shoots great. Plus, the twist will still stabilize the 52, 53, and 55s.


This
DNS  [Member]
1/18/2012 10:02:53 AM
Any truth to the rumor thats been going around on other forums, that shooting 55gr. bullets in a 1-7 twist will wear out the barrel faster than only shooting 62gr or above bullets?
EdgecrusherXES_45  [Team Member]
1/18/2012 10:09:47 AM
1/7 1/8 is what I run. Most mine are 1/8 twist never had a problem shooting any load.
Alpha-Romeo3  [Team Member]
1/18/2012 11:15:18 AM
Originally Posted By Brandon82:
Which do you prefer and why? Thanks in advance.

Get both.

I have 4 AR that are 1/7 and two carbines with 1/9, one of the 1/9 carbine is an AR with a heavy barrel and the other my Steyr AUG A1 16" medium contour barrel carbine.

With my 1/9 barrels I shoot from from 50gr to 69gr, 1/7 barrels 55gr up to 77gr ammo.

For defensive purposes I prefer my 1/7 carbine barrel with TAP 75gr ammo.

Here's a good reference for you so you could decide for yourself what ammo and barrel are better for your intended use.


http://ammo.ar15.com


thornejc  [Member]
1/18/2012 11:29:26 AM
It really depends on what you shoot. I honestly think if you are going to be shooting the 55gr or 62gr you will be better off with the 1:9. This kinda stuff varies from one weapon to the next so it is hard to give a comprehensive take on it. e.g. your LWRC runs a 1:7 twist and has fairly poor accuracy with cheaper lighter 55gr rounds while a cheaper Ruger with a 1:9 twist kicks them out fine. However, when using heavier 69gr rounds the accuracy of the LWRC was ridiculously good.

1:7 will probably be your more versatile twist rate but if you know you are just going to use lighter rounds (55/62gr) you will get more velocity and better ballistics with the 1:9.
PraesulPresul1  [Member]
1/18/2012 11:31:34 AM
1-7" or 1-8" barrels is all I ever buy.
ricochet7  [Team Member]
1/18/2012 11:56:27 AM
Originally Posted By DNS:
Any truth to the rumor thats been going around on other forums, that shooting 55gr. bullets in a 1-7 twist will wear out the barrel faster than only shooting 62gr or above bullets?


I have also heard this stated often and it MIGHT be true, it stands to reason that it could. I would think the difference would not be great, this matters little to most of us. Supposedly there have been tests, you would think this to be the case.

I own 1in9, 1in8, and 1in7 barrels and prefer the 1in7 and 1in8 due to their ability to handle heavies better. My 1in9 barrels shot 75 gr stuff ok, but not all do. Since I never shoot anything lighter than m193 (55gr) I can do without the 1in9 (even tho I may try some lightweights at some point).
Camaro822  [Member]
1/18/2012 12:21:54 PM
16" 1:9 for my 55gr ammo

1:7 is too fast. 1:8 would be ok, but not many of them out there.

anything heavier than 55gr would probably benefit from the faster twist
peligro113  [Team Member]
1/18/2012 12:26:27 PM
I have both and honestly it doesn't matter to me, I've shot 69g with my 1/9 and 45g with my 1/7 with no problems
PursuitSS  [Team Member]
1/18/2012 12:28:11 PM
Originally Posted By strm_trpr:
1/7 is preferred, it does better with 65+ grain ammo and t will be just as good with 55 grain, I have seen rumors that it can cause the jacketing to come off of really light varmint loads 40 grain and lighter, but I have no first hand experience with this. plus why use less than 55 grain unless you are doing target shooting.


On my duty carbine I have 1/12" twist. I ONLY carry Hornaday TAP URBAN 40 gn.

Much less danger of going through drywall.
Jbclark84  [Member]
1/18/2012 12:54:07 PM
1/7 I like the 75 gr PRVI match ammo.
Forest  [Moderator]
1/18/2012 1:29:25 PM
Originally Posted By PursuitSS:
Originally Posted By strm_trpr:
1/7 is preferred, it does better with 65+ grain ammo and t will be just as good with 55 grain, I have seen rumors that it can cause the jacketing to come off of really light varmint loads 40 grain and lighter, but I have no first hand experience with this. plus why use less than 55 grain unless you are doing target shooting.


On my duty carbine I have 1/12" twist. I ONLY carry Hornaday TAP URBAN 40 gn.

Much less danger of going through drywall.


Much less probability of stopping a violent threat too..
TSLtrek  [Member]
1/18/2012 1:49:26 PM
Neither my 1/7 CMMG nor my 1/8 Rainier Select shoot bulk 55gr well. My 1/9 Stag however does. YMMV
Tacticalbacon  [Member]
1/18/2012 2:51:10 PM
Originally Posted By Aggie1188:
It depends on what the rifles use is. 1/7 is great all around as you can use it for home defense with the larger bullets to stop those bastards. 1/9 is nice for the range cause you can use cheaper/lighter ammo to punch paper. IMO


If you're using an AR for home defense, do you really think the pairing of the proper twist rate with the larger bullets really matters??? Unless your home is as big as a football field, I don't think using a larger bullet in a 1/9 is going to affect the flight of the bullet much in the 10-20' that it is going to travel.
PursuitSS  [Team Member]
1/18/2012 3:20:28 PM
Originally Posted By Forest:
Originally Posted By PursuitSS:
Originally Posted By strm_trpr:
1/7 is preferred, it does better with 65+ grain ammo and t will be just as good with 55 grain, I have seen rumors that it can cause the jacketing to come off of really light varmint loads 40 grain and lighter, but I have no first hand experience with this. plus why use less than 55 grain unless you are doing target shooting.


On my duty carbine I have 1/12" twist. I ONLY carry Hornaday TAP URBAN 40 gn.

Much less danger of going through drywall.


Much less probability of stopping a violent threat too..


I seriously doubt that.

Two to the chest, one to the head. Tag em, bag em, their dead.
HeavyMetal  [Team Member]
1/18/2012 3:23:41 PM
1/7(or 8).

If I want a varmit gun, I will build a dedicated rifle.
Forest  [Moderator]
1/18/2012 4:16:50 PM
Originally Posted By PursuitSS:
I seriously doubt that.

Two to the chest, one to the head. Tag em, bag em, their dead.



FBI said the same thing when they were using their underpenetrating ammo prior to the Miami shootout. Look how well that turned out.
fuzzy03cls  [Member]
1/18/2012 4:22:36 PM
Don't care what twist rate. I use mostly 1:7 for only the reason that the higher grain ammo works better out of them. But I rarely have enough $ to buy that ammo. I shoot mostly 55gr & 62gr ammo. I notice zero difference in how it shoots 1:7 or 1:9. POA = POI in my shooting.
Forest  [Moderator]
1/18/2012 4:28:49 PM
BTW This is the link which contains that M193 (55gr) in a 1:7 data (at the bottom of the 1st post) Attack of the M193 Clones
BoovarBjarki  [Member]
1/18/2012 4:38:03 PM
All my AR type rifles are 1/7, my ACR has 1/9. With that said I do not notice a difference between them. However given the option I would prefer a 1/8 sorta jack of all trades barrel imo.
PursuitSS  [Team Member]
1/18/2012 4:43:06 PM
Originally Posted By Forest:
Originally Posted By PursuitSS:
I seriously doubt that.

Two to the chest, one to the head. Tag em, bag em, their dead.



FBI said the same thing when they were using their underpenetrating ammo prior to the Miami shootout. Look how well that turned out.


There is absolutely no correlation between 9mm 147 gn subsonic and .223 uber high velocity 40 gn. BTW, Hornaday LE division has stated no one has ever survived a torso shot with .223 TAP Urban!
Forest  [Moderator]
1/18/2012 5:04:37 PM
Originally Posted By PursuitSS:
There is absolutely no correlation between 9mm 147 gn subsonic and .223 uber high velocity 40 gn.

Insufficient penetration is insufficient.

BTW that 147gr Silvertip has MORE penetration than the 40gr TAP...





BTW, Hornaday LE division has stated no one has ever survived a torso shot with .223 TAP Urban!


As an LEO you know people can be shot and survive long enough to hurt/kill others (again see the Miami Shootout). It's about stopping the threat as fast as possible. Remember they are trying to sell something - they have much better options available, they just cost a few dollars more per box.
Brandon82  [Member]
1/18/2012 5:37:03 PM
1/7 seems to be the most versatile.
senone  [Member]
1/18/2012 7:30:53 PM
Originally Posted By PursuitSS:
Originally Posted By Forest:
Originally Posted By PursuitSS:
I seriously doubt that.

Two to the chest, one to the head. Tag em, bag em, their dead.



FBI said the same thing when they were using their underpenetrating ammo prior to the Miami shootout. Look how well that turned out.


There is absolutely no correlation between 9mm 147 gn subsonic and .223 uber high velocity 40 gn. BTW, Hornaday LE division has stated no one has ever survived a torso shot with .223 TAP Urban!



Amen....

Krinkplinker  [Member]
1/18/2012 7:39:14 PM
Originally Posted By senone:
Originally Posted By PursuitSS:
Originally Posted By Forest:
Originally Posted By PursuitSS:
I seriously doubt that.

Two to the chest, one to the head. Tag em, bag em, their dead.



FBI said the same thing when they were using their underpenetrating ammo prior to the Miami shootout. Look how well that turned out.


There is absolutely no correlation between 9mm 147 gn subsonic and .223 uber high velocity 40 gn. BTW, Hornaday LE division has stated no one has ever survived a torso shot with .223 TAP Urban!



Amen....



I think forest demonstrated his point rather effectively in his last post. That being said, I wouldnt be reaching for the AR as my first choice for home defense either. 12ga all day long.
PursuitSS  [Team Member]
1/18/2012 7:52:05 PM
Originally Posted By Krinkplinker:
Originally Posted By senone:
Originally Posted By PursuitSS:
Originally Posted By Forest:
Originally Posted By PursuitSS:
I seriously doubt that.

Two to the chest, one to the head. Tag em, bag em, their dead.



FBI said the same thing when they were using their underpenetrating ammo prior to the Miami shootout. Look how well that turned out.


There is absolutely no correlation between 9mm 147 gn subsonic and .223 uber high velocity 40 gn. BTW, Hornaday LE division has stated no one has ever survived a torso shot with .223 TAP Urban!



Amen....



I think forest demonstrated his poiynt rather effectively in his last post. That being said, I wouldnt be reaching for the AR as my first choice for home defense either. 12ga all day long.


I'll take real world shooting data over ballistic gel anyday. As to a shotgun, when I have to pull the trigger inside someones home, I don't want to risk killing someone who is behind a wall and is an innocent bystander. The street isn't a video game, if you accidently kill someone you can't hit reset.

BTW, I know of at least two SWAT teams that use TAP Urban as their entry round.
Evile  [Team Member]
1/18/2012 8:39:10 PM
Something like 60years of battlefield experince has gone into the ar15 platform and that has led to the 1/7 twist..... Why use any thing else? Save for varment or target
jwb47  [Member]
1/18/2012 9:07:11 PM
I have 1/7 , 1/9 , and 1/12 twist rifles ar15's , mini-14 , and bolt guns . I have tried 52,55,62,68, and 70 grain bullets. the 1/7 twist shoots all acceptable and most excellent . the 1-9 twist barrels vary I have a 20 inch bushmaster that refuses to shoot anything over 62 grain worth a crap while suprisingly enough my 11.5 inch dpms barrel on my full auto does great from 55 up to 68 graiin . I have a 16 inch carbine 1/9 twist that handles 53 grain up to 68 grain great and 70 grain barnes well enough . my 1/9 mini -14 likes the 52 grain hornady amax and hornady 75 grain match bullets . my 1/12 varmint rifle starts to key hole with anything past 60 grains but 52 grain hornady amax bullets will make one nice raggedhole 5 shot groups.
if I was limited to just one rifle I would grab my colt 6940 since it can do well with about any load I toss at it. I vote 1/7
Shay_Ellafrits  [Member]
1/18/2012 9:20:22 PM
I had a 1-9, didnt stabilize the ammo I used, so i switched to a 1-7, and from now on, all my ARs will have a 1-7 twist.
B44T  [Member]
1/19/2012 3:19:03 AM
From memory. ( sorry, my notes are not available at the moment )

During the SAW trials the minimum trace distance for the 5.56 was changed from out to 600M to a minimum of 800m, a new longer tracer that would become the M856 was developed to meet the new requirement.

The SS109 later adopted as the M855 was required to penetrate a US steel helmet at something like 500 meters.While 1 in 9 twist proved ideal for that bullet and purpose, the the new tracer due to its length, needed a faster twist. 1 in 7 did the trick and the rest is history.

Pic from the web.


M193 Ball , M196 tracer (red tip) M855 Ball (green tip) M856 Tracer (orange tip), SMK

ETA
Corrected syntax and spelling.
NWCP  [Member]
1/19/2012 4:27:40 AM
I prefer the 1 in 9 5.56 AR that is both reliable and effective against the little furry critters that I originally bought the gun to go after and the bullets that work best in the rifle tend not to over penetrate yet will stop an intruder if so required. Anything needing a heavier bullet gets the 6.8SPCII treatment.
RowlandP  [Member]
1/19/2012 6:23:10 AM
The US Army argued for a 1:9 twist when the M16A2 was evaluated. They cited that the least amount of twist needed to stabilize a bullet was preferred. Slower rifling produced less bullet stress, less barrel stress, prolonged barrel life, and less fouling. They also cited the factt hat less stabilization increases terminal balistics. (It's interesting that the M16 in Vietnam was known for creating wounds out of proportion to its caliber but when a faster twist was adopted the bullet was known for zipping straight through with sometimes little effect.)

1:7 was adopted by the Marines since is was consistent with the twist on the squad automatic weapon. However, the Marines wanted a twist to stabilize long tracer rounds. The Army's position was to not want a barrel that was made to stabilize marking rounds, but rather to stabilize the killking rounds. The Army found the 1:9 superior for M192 and M855 ammunition.

1:9 may not be what they got, but its what they wanted.

In my experience, there is no practical difference in accuarcy between a 1:9 and 1:7 at most range ranges. 1:7 may stabilize longer bullets better for better accuracy at longer ranges. If shooting 55-62 grain out to 300 yards or so, 1:9 is as good or better.

In case anyone wants to read the Army evaluation...
http://www.dtic.mil/dtic/tr/fulltext/u2/a168577.pdf
bigjunk1  [Member]
1/19/2012 7:36:05 AM
1/7 and 1/9 vary from rifle to rifle because the companies either round up or down and don't follow an exact formula per inch. If you actually measure the turns per inch some 1/7 and 1/9 end up being the same.
A Colt 1/7 may end up being 1/8 but it is marked 1/7 and a LMT may be 1'8 and marked 1/9. You need to actually measure your turns per inch and not just read the label to know what you have.
TinMan2  [Member]
1/19/2012 8:37:06 AM
I have Two AR's both are 14.5" barrels. One is 1/9" and the other is 1/7". My range only goes to 400m. Both shoot good if not excellent to 300m. The 1/9 and 1/7 twist both have a problem with 55gr at 400m, groups really grow. At 400 the 1/7" really comes into its own with LC 62gr penetrators showing fist sized groups. The 1/9 still groups poorly at 400m with LC 62gr. I do not use optics, irons only. I do 99.99% of my shooting under 250m but if I was choosing only one AR using the ammo I shoot and what I experienced it would be 1/7". Ps. The 1/7" does poorly with the. 22 rimfire kit and 1/9" shoots. 22lr super.
Man_On_Nickel  [Member]
1/19/2012 8:45:14 AM
I shoot M193 and 1/9 does that best - at least in my hands. I like 1/9.
TARFU  [Member]
1/19/2012 9:22:24 AM
Best (most accurate) load in my 1:7 and 1:8 is a 52 gr. SMK