5.56 twist rates

[Goat]

I am in the market for an AR and have pretty much settled on the Rock River Predator Pursuit 16"Carbine or the Coyote Carbine also in16". The Predator has a 1:8" and the Coyote a 1:9". What weight bullets can be expected to stabilize in the different twist rates?
Goat

[AJMD429]

I never tried over-55-grain bullets in a .223, but I'm sure some folks on here have, and will chime in with real-world information.

One side-note is that IF you ever plan to add a suppressor, the best results are going to require subsonic ammunition, which slows the RPM attained with any given twist, and can be a problem, especially with the often heavy-for-caliber bullets those folks use. So they use higher-than-average twists sometimes. The other side of the coin is that those faster-than-needed twists may not be ideal for accuracy either.

One good thing is that it doesn't cost all that much to have a separate upper for different tasks or even loads, or for even less cost, it is very easy (even for a kitchen-table-bubbasmith like me) to replace a barrel on a given upper with one you find you like the twist rate better.

[Chris83716]

1 in 9 is usually able to handle up to 69 grain bullets if the velocity is high enough. The 1 in 8 is designed for the 77 grain and 80 grain match bullets and may blow up some of the thiner skinned bullets.

Chris

[Goat]

AJMD429, just what is involved in changing a barrel? I had not even thought of that at all. Is there a website that I could be directed to that would give me such information? This AR-15 thing is getting more and more interesting.....
Goat

[Goat]

Thanks Chris! I was needing just that kind of info.
Goat

[RustyJr]

I personally prefer a 1:9 twist because in my experience it seems that the 1:9 handles the 52grain to 69grain loads better and since in my area the two most common grains that are available at a cheap price are 55 and 62 grain it works well for me.



RustyJr

[AJMD429]

AJMD429, just what is involved in changing a barrel? I had not even thought of that at all. Is there a website that I could be directed to that would give me such information? This AR-15 thing is getting more and more interesting.....
Goat

There is an AR-15 forum, but I honestly think you'll get better advice here, if you're patient; too many hot-shot types on the other forums who bluster in with know-it-all answers that aren't always right and/or practical.

There is a special wrench ($20 maybe) you need that fits all the little cutouts in the collar around the barrel. As far as I know, being 'milspec' they are pretty much all interchangeable, even between brands, without headspacing issues.

[Hobie]

I have a 1:9 twist barrel but it seems to stabilize the 77 gr. MK just fine. My old SP1 with those old slow twist barrels stabilized the 73 gr. Sierra semi-pointed just fine. It may be that both these barrels just happened to be be a bit faster twist than supposed by the makers.

[Streetstar]

Mil-spec is 1:7 and has been for awhile, but , as stated previously, is mainly for shooting heavy for caliber projectiles. The older M-16's and older Colts are 1:12 to stabilize 55 gr projectiles --- a lot of bolt action varmint rifles are 1:12 also, with some being 1:14.

1:9 has been used as a compromise twist rate to bridge the gap a little --- i have several 1:9 rifles and they seem to shoot most of the popular bullet weights from 55gr to 69 grain pretty well --- i haven't tried it with heavier bullets and shoot 55 gr FMJ's most of the time for plinking. And my 1:7 twist rifles work ok with 55 grain too interestingly enough, but then again, my rifles are not precision target rifles, -- they are either "fun guns" or defensive oriented guns that have maybe 1.5 MOA potential at best

1:8 twist seems to be preferred by some very reputable manufacturers (LaRue is one) that use this twist in target grade rifles---- some guys shoot these things at 600 yards or more and the heavier bullets are a bit better for this type of stuff --- also a 1:8 twist is often had with a .223 Wylde chamber design that is a bit more precise than a standard 5.56 chamber. The Wylde chamber lets you use either 5.56 or .223 i believe, but i have been told that it is generally not recommended to shoot 5.56 ammo in a .223 chamber , but i am sure it gets done all the time


Changing barrels is not that hard, but definitely not something i would personally want to do often ---- the last time i tried was on a factory fitted upper assembly and the FSB (front sight base ) pins were so tight i just said heck with it, and bought a new stripped upper housing to install the barrel on. I also have a tendency to just throw money at problems until they go away too, but i have to say, working on AR-15's is about as easy as it gets for an amateur as long as proper install protocol is followed and proper torque specs are used

An AR-15 is entertaining because you can have a gun case full of 5 different upper assemblies for different applications, and use them all with the same lower just by pulling a couple of pins and

[madman4570]

Both my 1991 Colt #6601 Match HBARS have 1:7 TR
They shoot the 55gr up to 77gr absolutely wonderfully.

To choose one rate-------------------------1:7(for me at least)

Both will hold (with 55gr FMJ handloads off bench/sandbags----under 1MOA open sights)as well as the heavier bullets,though match 55grainers flow threw mine the most).
Can't speak for any other guns other than mine??????????
They actually(most the time)group about as well as my model 70's/Ruger#1's with scopes

It is absolutely amazing what you can do with open sights provided the rear aperture and front post are made for task at hand.
"IF" you have the eyes--------.034(post) .034(aperture) I am very lucky(my eyes still extremely good----20/15)
The .034 aperture will insist on same cheek weld/eye relief distance (every time)or--------you will easily know

[Chris83716]

Goat,

It is easy to change an Ar barrel and can be done at home in with some very basic tools. Most people just buy an additional upper and swap uppers rather than change barrels. I did this for about 5 years with my match upper for CMP/Highpower and a flat top with a scope for shooting whistle pigs.

Chris