Why 1:9?

[MTMilitiaman]

So I'm not a huge fan of the poodle shooter but every once in a while I get to window shopping because I guess I figure if I could find an AR that was acceptable, I wouldn't have to skip 80% of the gun rags on the shelves these days. Seriously 3/4 of every gun magazine is dedicated to ARs so if ARs aren't your thing, only like a page and a half out of every magazine applies to you.

So I am browsing the Ruger website, looking over their SR-556. Seems like a pretty solid rifle. Held one at an FFL dealer not too long ago, and that is what peeked my interest. Get to the part where it says 1:9 twist, completely lose interest. And that's how it goes.

I don't get it. Why put a varmint rifle twist on a fighting rifle? This rifle is obviously set up for defense and marketed towards that genre. All 5.56mm fighting rifles have 1:7 twists. If you want to set up an AR for ground squirrels and coyotes, then maybe a 1:9 twist is appropriate. But for this type of rifle, a 1:9 twist has absolutely no advantage. None. Big DOH! :banghead: on Ruger's part. I don't understand how big companies like Ruger have people on payroll specifically to make sure this stuff doesn't happen, but it still does. Hope someone lost a Christmas bonus for that mess up. I have two or three Ruger firearms pretty high on my "To Get" list, the SR-556 isn't one of them, and won't be until they get serious, stop messing around with the 1:9 twist rates.

[/end rant]

 

[MistWolf]

Why worry about it? If the Ruger doesn't offer what you want, move on to a maker that does

 

[TurtlePhish]

I don't see the huge problem with 1:9...

Sure, 1:7 handles heavier bullets better, but 1:9 is capable of handling almost any common load fairly well. Remember that the original M-16 had a 1:12 twist rate and managed to have perfectly acceptable battlefield accuracy.

 

[longdayjake]

So, you want to shoot tracers? Cause that is really the only reason you would need a 1:7 twist from a 16" AR. If you want a heavy bullet shooter you shouldn't get a 16" AR anyway.

 

[Jackal]

I have fired everything from 40gr through 72gr from 1:9 barrels. They work great for everything. I have not seen a difference in practical accuracy or performance between my self built 1:9 AR vs my Spikes 1:7 using 69gr rounds. As long as the bullet is stabilized, it does not matter. If a 1:12 stabilized a heavy round (which it does not!) it would be acceptable as well. Bottom line, 1:9 is the most versatile, firing everything from 40gr through 72gr without keyholes and with above par accuracy. Want to pop that coyote with a 45gr hp? Want to target practice out to 400 yards? 1:9

 

[Nevmavrick]

What's the difference? A "fightin' rifle" when in actual use is used to cause dirt to jump around a tin can that's so close that if it DID get hit, it'd have powderburns. "Here...hold my beer and watch THIS!"
If you really want to do some careful shooting, you'll find 1-9" will do just fine.
Most of the ammo you bump into is 55gr, anyway, so it won't make a lot of difference.
Yes, I'm one of those elitist bolt-action shooters, but I DO support YOUR right to buy ANYTHING you choose, and use it anyway you wish...safely!
Have fun,
Gene

 

[Tommygunn]

1:9 is not just for varmints.
It will hand 55 grain bullets, that's what it was meant for. It will also handle heavier (actually longer) bulklets as well, and seems to be the best compromise for civilian shooters.
1:7 is mil spec and is geared for heavier (longer) bullets.
But remember we went through Vietnam with 55 grain M-16 ammo.

Anyway just because Ruger put a 1:9 twist on one of their ARs doesn't mean they "messed up."
But as has been said, if you want a "mil spec" 1:7 then there are those out there...BCM. Noveske, Colt......

 

[joed]

I'm not a fan of the .223 because of all the various twists it comes in. For awhile I owned a Savage 10fp in this cartridge. Bought it for varmint hunting. Because of the 1-9 twist it shot 69 gr bullets with fantastic accuracy, but anything lighter would open the group. I ended up selling a nice rifle because it was worthless for what I wanted. I purchased a .22-250 and haven't looked back.

I do own a .223 as a necessity in an AR. Back in May I started looking at various brands. At that time most came with a 1-9 twist except Colt which came in 1-7. So, I bought the Colt and put it in the safe for the day I may need it.

But, fast forward 4 months and now every maker is offering 1-7 twist. I honestly believe this cartridge will be shooting a 200 gr bullet at 900 fps from a 1-4 twist barrel by next year.

I am not a fan.

 

[UKWildcats]

I have multiple 1 in 9 -- 3 are set up for Prairie Dogs, and 2 AR's -- 1 in 9 is a great compromise twist that will allow you to shoot low weight high velocity bullets without tearing the jacket off along with heavy weight bullets for longer range/bigger game.

You have to be a little careful with the low weight bullets to keep velocity down so that you do not blow the bullet up due to high rate of spin though.

Link give great data on 223 Cartridge Data -- http://www.6mmbr.com/223rem.html

With a 1 in 7 you will have to shoot the heavier weight bullets that have a strong jacket -- no problem with that but it will limit you a little -- the 223 does give you a lot of choices and with the AR you can just get a different upper to shoot heavier/lighter bullets.

UK

 

[MachIVshooter]

You do not need 1:7 for common .223 loads from 40 gr. to 62 gr. 1:9 will handle bullets up to 70 grs. just fine, and anything heavier is either too long to fit in an AR magazine or seriously encroaching on powder space.

 

[HorseSoldier]

So, you want to shoot tracers? Cause that is really the only reason you would need a 1:7 twist from a 16" AR.

+1. The 1:7 twist was necessary specifically for the use of the M856 tracer round. If I remember right, 1:9 was actually found to be better than 1:7, in terms of accuracy, for standard M855/SS109 ammunition, but would not effectively stabilize the tracers. Some people have reported issues with 1:9 stabilizing 70+ grain ammunition, but it doesn't seem to be a universal, for whatever reason.

 

[cfullgraf]

1-9 twist barrels in 223 Remington are a good compromise and handle a wide range of bullets.

I have several ARs with 1-7 twist barrels, both Service Rifle match rifles and varmint rifles, and they shoot 55 grain bullets accurately and without issue. I never tried them with anything lighter. Nothing new, i obtained/assembled the rifles over a period five to seven years ago.

I save the 40-50 grainers for 22 Hornet and 221 Remington Fireball.

 

[Cosmoline]

It will hand 55 grain bullets, that's what it was meant for.

That's 1:12, which IIRC was the twist rate for the M16's in the Vietnam era. The 1:7 is the modern M16 twist for the heavier ball. 1:9 is not military. The tracer explanation is about the best one I've heard. And I haven't noticed an accuracy difference.

 

[Jim Watson]

longdayjake and Horse Soldier have it right.
The USGI 7 twist is for the tracer.
A 9 twist will handle ball and probably the various gimmick loads currently on issue.
The dividing line seems to be about 75 grains of lead core bullet. Some 9 twist barrels will handle them, some won't. A friend has one that is marginal. 75s are stable but less accurate than 68s... in calm air. But if the wind is blowing the heavier bullet wins.

 

[SSN Vet]

I can see other factors that will come into play as to whether a bullet of any particular mass is stabilized.

barrel length...

chrome lining...

load particulars....

 

[jmr40]

Not all AR's are set up as fighting rifles. They are being used quite a bit as varmit and deer hunting rifles. Most bolt guns are dedicated varmit rifles with a 1:10 or 1:12 twist. The 1:9 is a decent compromise that shoots all weights fairly well.

 

[Oglee]

Actually the very first AR-15's(before the Army adopted them and named them M16) was issued to ARVN troops and SEALS with a 1/14 twist rate.

When the Army was looking at adopting them(while also trying their darndest to make the rifle fail) the found that supposedly the 1/14 twist would not stabalize the M193 ball ammo in arctic temps well enough that eventually it got changed to 1/12.

When they released M856 the round was to long to stabilize in anything other than 1/7 so that eventuall became the twist rate, which now with ammo like M855A1 and the 70gr TSX the 1/7 is actually needed due to the length of the bullets.

 

[rcmodel]

If you want to set up an AR for ground squirrels and coyotes, then maybe a 1:9 twist is appropriate.

NO, actually a 1/12 would be approiate for that.

The 1/9 is the best compromise in bullet selection, barrel life and accuracy the manufactures can possibly come up with.

1/7 is not needed for any normal civilian bullet weight or length.
And it over-stabilizes lighter varmint bullets to the point of them possibly disintegrating in mid-flight from the excessive RPM.

rc

 

[ATLDave]

What bullet weight will you actually be shooting? If you're going to shoot 55gr, some people claim better accuracy with a slower twist. I have a 1-in-7, and it strongly prefers bullets of 62 grains and up, and 69 grain is better than 62 with it. That's great if I want to make up some match-grade ammo. If I want to run through several magazines, though, I've got to sacrifice accuracy to go down to affordable plinker ammo.

If you're mainly going to be doing carbine-y stuff with it, one might affirmatively prefer the 1-in-9 twist.

One other point: as I understand it, the 1/7 twist requirement was needed because of heavier bullets in the m4's shorter barrel of 14.5 inches. IIRC, the Ruger has a 16+" barrel, which may further reduce the need for super-fast twist.

 

[EMS_92]

Horse Soldier bout nailed it.

 

[MCMXI]

1/7 is not needed for any normal civilian bullet weight or length.
And it over-stabilizes lighter varmint bullets to the point of them possibly disintegrating in mid-flight from the excessive RPM.

Noveske seems to favor a 1:7 twist for 16" barrels and a 1:8 twist for 20" barrels. I'm sure they want their barrels to work for bullet weights from 55gr to 80gr.

http://noveskerifleworks.com/cgi-bin/imcart/display.cgi?cat=123
http://noveskerifleworks.com/cgi-bin/imcart/display.cgi?cat=171

Both of my AR15s have 1:8 barrels but I don't shoot bullets lighter than 55gr and typically I shoot a 77gr SMK.

 

[MachIVshooter]

I can see other factors that will come into play as to whether a bullet of any particular mass is stabilized.

barrel length...

chrome lining...

load particulars....

No, no and, for the most part, no.

Barrel length really has nothing to do with bullet stabilization so long as it's no so short that the spin isn't effectively imparted (bullets skipping the rifling).

Chrome lining affecting accuracy has to do with tolerance. Chrome lined bores are oversized prior to the lining and, if the chrome is not perfectly applied, remain oversize. Chrome or no chrome, a sloppy bore won't properly stabilize any bullet, regardless of twist rate.

By load particulars, I presume you mean velocity. Slower moving bullets, especially stubby ones, require lower RPMs to stabilize. That's why most handgun and Black Powder twist rates are very slow (like, 1:16 all the way to 1:60). However, spinning a slower bullet faster won't make it less stabile. The only time twist rates are too fast is when shooting lightly constructed bullets at very high velocities. Many a shooter years ago found this out trying to run .22 Hornet bullets (meant to withstand ~130,000-150,000 RPM) in faster twist .22-250 or even .220 Swift rifles and had them cooking at well over 200,000 RPM. The bullets simply come apart from centrifugal force.

 

[Jeff H]

Not all AR's are set up as fighting rifles. They are being used quite a bit as varmit and deer hunting rifles. Most bolt guns are dedicated varmit rifles with a 1:10 or 1:12 twist. The 1:9 is a decent compromise that shoots all weights fairly well.

+1. My all purpose AR is a 1:9 and shoots most everything good. My NM AR is 1:7 for the heavier bullets required for shooting 600 yards.

 

[WVRJ]

Mine with a 1 in 9 shoots 55 to 70 grainers just fine.Anything heavier/longer will eat up some powder space.A 16" barrel would turn some pretty mopey velocity numbers with the real heavy bullets.I settled on 60 gr ballistic tips and have been tickled poopless ever since.

 

[ugaarguy]

1/7 is not needed for any normal civilian bullet weight or length.

Once again I'll remind y'all that civilian demand for Black Hills Mk262 Mod1 overruns so outstripped demand that Black Hills made it a regular factory commercial offering. Y'all are also ignoring the huge swell in the market of copper solid bullets, which are longer for weight than conventional copper jacketed lead core bullets.

You do not need 1:7 for common .223 loads from 40 gr. to 62 gr. 1:9 will handle bullets up to 70 grs. just fine, and anything heavier is either too long to fit in an AR magazine or seriously encroaching on powder space.

I'm sorry, but that's false on a couple of counts. First, conventional construction bullets up to 77 gr easily fit an AR magazine, and do not encroach on powder space to any significant degree. Second, there's been a shift in recent years as to which bullet weights are common in .223. Common loads are now 55 to 69 grains, and every major ammo manufacturer offers a 75 grain or heavier load.