Best twist rate for AR?

[Cokebottle]

im guessing 3 seperate lowers to make 3 ar's for each twist. 1:7,1:8, and 1:9... why? i dunno, i personally think if your gonna get a barrel for anything, its either go with A, B, or option C for the compromise of the two. but getting all three is silly. My CMMG upper is in 1:7 because eventually i plan on handloading my .45 for cost and 5.56 for distance. but thats just me.

I have four.
One is complete. That's a 14.5" (pinned FH) Daniel in 1:7
The second one is the original Calguns state outline lower. Originally, I only planned to build one, but then I started wanting one in FDE/camo, and I didn't want to adulterate the Calguns lower, so I picked up an LRPB from a group buy.
The Calguns state outline was slated to be an A2 clone (except with a flat top.) Even though they aren't the best, I was planning on putting a Stag 4H upper on it. That's a 20" 1:9.
But now, with the pending obsolescence of the high-cap law, I've decided to go featureless with it to be able to have some fun with 30 rounders.

But that's okay... JD did another run of Calguns lowers, so I picked up a California Bear (which is what I originally wanted last year). That one will probably be a featured 18" barrel.

The 4th lower is a pistol lower that I machined from an 80%.

[Cokebottle]

Ok so I've been watching this and have been kinda surprised at the answers.. I have asked this a few months back on 3 different forums even this one and was heavily told to go with the 1:7... Now I'm seeing once someone says one thing a ton of people agree not to have an argument and chance looking dumb or have one so assume it's best to recommend it to others..

A part of that is the "bandwagon" effect... but the biggest part of it is that the high quality barrels are all 1:7 (not including the 1:8 match barrels, which includes the entire LaRue line).
Common 1:9 barrels are Rock River, Stag, Delton, etc.... Not exactly top of the line stuff. Noveske, Daniel, and all of the other high quality chrome-lined and hammer-forged barrels are 1:7.

The one that surprised me was the Ruger SR556. It comes with a 1:9. I don't know if they are making their own barrel or buying it.

[Jasonaspears]

Thanks for all of the info guys. I settled on a Spikes Tactical Midlength LE with the 1:7 twist

[DannyInSoCal]

Find yourself a 1/11 twist (In a 6.8....)

[1norcalvarmintHunter]

Twist rate is overrated...

[CK_32]

While I've seen a 7 spin the jacket off a 55gr bullet, it's not that common. as for the stability:

Anyways, I have a 7 that doesn't spin jackets off m193. That's all I need.

I agree, cheaper .223 ammo ,So im told with thin jackets seem to be the bullets that seem to burst and peel the jacket off of the 55gr or lighter rounds. But with Military FMJ rounds with 5.56 rounds have thicker jackets on them reason the military has no problems shooting lighter bullets..

You mean to say it will most likely be 1:9, as most are 1:9 chome-moly (no chrome lining).

I tend to spoil myself. I own two ARs. One for running and gunning and one that has a primary role of precision shooting while still being able to double as my backup CQB rifle. The M4 rifle which I use for running and gunning has a 1:7 chrome lined barrel. The Recon rifle which is more of a bench rest whore has a 1:8 stainless steel barrel.

I rarely spend the money on the high-end match grade ammo that they can handle, but it is nice to know they can handle it when I do.

Here is a more realistic way of looking at it....

If you want a precision AR for bench rest shooting or marksmanship competitions then you want 1:8 stainless steel. Stainless steel offers more precise rifling because it is softer and thus easier to cut. If you are going to spend the money on a stainless barrel, then it is just silly to get it in 1:9. However, it is a complete waste of money to get a stainless barrel on an AR that is going to be used for CQB, because you will be replacing the barrel constantly. That softness that makes it easier to cut and gives it more precise rifling, also makes it wear out faster. In precision shooting you take fewer shots, and take your time inbetween them. In CQB you put as many rounds on target as fast as you can. So stainless is the right tool for precision shooting and wrong tool for CQB.

If you want a run and gun CQB rifle you want some sort of chrome lining or WASP coating because you are going to be putting as many rounds on target as fast as you can. That heat and that amount of friction wears down a standard barrel too fast. So you need some sort of lining or coating to make it last longer. A 1:7 chrome-lined barrel costs the same as a 1:9 chrome-lined barrel, so you take the upgrade because it just makes sense money wise. What you can in accuracy from the twist rate you often loose however from the coating, as it causes minor imperfections in the rifling.

If you just want a plinker for the range, and you are probably only going to go shooting every once in a while, and not going to be taking carbine courses every other month and you are not going to be competing in any matches then a standard 1:9 chrome moly barrel will serve you just fine.

That is the practical way of deciding which type of barrel will serve you best.

Well said^

So it seems like it's been established that 1:7 seems more versatile, with the caveat that with extremely light bullets (45gr varmint rounds)- it's possible to spin the jackets right off. What are some other cons of the faster 1:7 twist rate? Do the barrels wear out faster?

Also, I've read somewhere that the original M-16 as designed by Stoner had a 1:12 twist rate, and the whole idea behind that relatively slow twist rate was to purposely have unstable bullets leaving the muzzle - an attempt to get more wounding potential from the tiny 55gr bullets (compared to the standard 147-150gr bullets coming out of an M-14 or M1 Garand) Any truth to this? Or pure FUD?

Thoughts on RRA? Most of their barrels are 1/9 except for some of their stainless which are 1/8. I thought that they were one of the better companies. Thoughts?

Also, many are not chrome lined, or have it as a option(except for the stainless, of course). Sorry if I am adding some more questions to the OP's post, but for a first build, do I need to go chrome lined?

RRA and Stag spikes to name a fraction of companies.. Seem to use 1:9 for god who knows.. but like I said its usually seen on base line or smaller companies AR's. Cheaper.. Maybe.. Idk cant tell you why.. But I have noticed a lot of higher more respectable (Not saying the others arent) but companies well trusted like DD,LMT,Knights,BCM ect. seem to use 1:7.. Kinda of a trend going on there no? Maybe its because they have been around longer and are still use to the old ways and the new guys found some trend with 1:9.. But thats just something to keep in mind.. If all these other companies Honda, Acura, bla bla bla.. Use v6 motors.. and ferarri and lambo and BMW use V8s... What would you rather go with if you had the choice.. Again just a reference not saying these other companies are lower end.. But they are no where near as trusted or have the name as DD,BCM,Noveske ect.

[diginit]

Depends upon how much you want to spend for ammo. Not too many ranges are over 100 yrds.

[Cokebottle]

Kinda of a trend going on there no? Maybe its because they have been around longer and are still use to the old ways and the new guys found some trend with 1:9.

1:9 is not a "new trend".
The original M16A1 was a 1:12 twist. Worked fine for the military until they went with the longer tracer rounds. Rather than mess around with 1:9, they went directly to 1:7 as a "do it all," but remember that they aren't shooting 45-55gr PWC .223... they are shooting 5.56, generally 62gr and heavier.

. But thats just something to keep in mind.. If all these other companies Honda, Acura, bla bla bla.. Use v6 motors.. and ferarri and lambo and BMW use V8s... What would you rather go with if you had the choice.. Again just a reference not saying these other companies are lower end.. But they are no where near as trusted or have the name as DD,BCM,Noveske ect.

That is a valid comparison ONLY in that each has their purpose (and Lambo uses a V12).
Not everyone needs a BMW or Lambo... and a Honda or Acura is not suitable for everyone either (well, the Acura NSX is a pretty damned nice car).

As mentioned before, the "best" twist rate depends on what ammo you are using. For 99.9% of civilians, 1:9 is perfectly suitable. 1:7 is simply not needed shooting 45gr to 62gr .223/5.56, and the faster spin rate does introduce accuracy issues. The bullet will drift in a spiral path which will gradually widen. At typical range ranges from 100-300 yards, it is not that extreme and can be compensated for, but at longer ranges, the lighter bullet will drift farther and result in horrible groupings.

There's a reason that match shooters use 1:8. It is matched perfectly to the ammo that they are using for precision shooting.
If 1:7 were so much better, like the V8 in the BMW, why would match shooters not use it?
Why not go to a 1:5 twist if 1:7 is better than 1:9?
Because it's not. 1:9 is "better" for 45-55gr ammo.
1:7 is "better" for 75 and heavier.
62gr will shoot just fine out of either.

You can't go by what the manufacturers offer. They simple respond to market demands. The bandwagon wants 1:7 because that's what the M4 uses (on a 14" barrel BTW), so the manufacturers, even those without government contracts, offer 1:7 twist.
There are only a few actual manufacturers of barrels, while there are dozens of companies that offer them.

[markw]

I just got a 1:22/7 twist rate barrel and I gotta say, it runs circles around all the other stuff out there.

Giggity.

Heh, someone just got out of math class.

[Cokebottle]

Heh, someone just got out of math class.

He's talking about the new progressive twist.
It starts at 22 at the chamber to reduce wear, and tightens to 7 at the muzzle

[freonr22]

Have 14.5" 1/9 bushmaster. Colt 20" 1/12. Lmt cryo'd (all lmt's are) 16" 1/7 upper. Have not shot them to compare. What weights should I reload/buy to compare them?

[SixPointEight]

I agree, cheaper .223 ammo ,So im told with thin jackets seem to be the bullets that seem to burst and peel the jacket off of the 55gr or lighter rounds. But with Military FMJ rounds with 5.56 rounds have thicker jackets on them reason the military has no problems shooting lighter bullets..

Actually, military fmj has a thinner jacket than most m193 type bullets by commercial manufacturers, like Hornady, Remington etc.

[SoCalG]

Just my input. (I'm learning about the twist rates, I'm certainly no expert) Assuming you wanted to just get your first AR and just go shooting, seems like the best bang for the buck or most common twist in civilian AR's is a 1:9. I think most of us here can agree that you will catch the AR "bug" and want to build another one very soon after the first is completed. I'm building my first AR right now. I already know I want 2 -a tactical AR and longer range (sniper) AR. From my reading here and other AR websites, I already know that I will need a longer barrel/different twist for the sniper version from my tactical version. Deciding NOW if you're going to build 2 different AR's may answer the question for alot of us in regards to the barrel twist to choose.

I do have a question for the "experts". From reading the differences between all three twists - why not go with a 1:7 which gives you practically the spectrum? Seems like this would give you more options as to ammunition you can shoot. (excluding people who re-load themsleves with a specific bullet spec in mind)

[SoCalG]

Somebody posted a link to this website in regards to the twist rate discussion. See below for his post - I think this guy makes some great points. Read the bold section!(makes alot of sense)

from http://mscg.yuku.com

Bullets must have enough spin (RPM) when leaving the bore in order to fly true. Remember bullets begin to slow down (in RPM and velocity) from the moment they leave the bore so they must have enough spin from the start so that they remain spinning enough to fly true over the course of their trajectory otherwise if they arent spinning enough they will start to wobble off course which can result in a complete miss. (Remember misses are bad.)

Barrel twist rates are calculated using the caliber of the projectile and the length of the projectile. Most think in terms of weight of the projectile that determines twist rate but it is really the length. And in general terms the longer the bullet given the same caliber the more it will weigh but the truth is you could have two bullets that weigh the exact same amount but if one has an aluminum core it will be longer than the one with a lead core so the lighter bullet BECAUSE it is longer will require a tighter twist rate than the heavier/shorter one will.

The M16 started off with a 1x14 twist which is enough to shoot 55 grain bullets as long as the temperature of the air was above freezing. If the temp was below freezing the air density was such that the 1x14 twist was too slow and the bullet lost its spin too fast resulting in misses.

So the military changed the rate to 1x12 which solved the problem.

Then comes along the SS109/M855 62 grain round which since it is a longer bullet (because it is heavier) requires a 1x10 to stabilize. Problem was the tracer ammo M856 is even longer than the ball round of the SS109/M855 ammo cause they packed it with enough tracer compound so the bullet would trace all the way out to 800 meters which it almost twice as far as the older tracer ammo that burnt out at around 450 meters. Consequently this newer tracer ammo is a LONG bullet and requires a 1x6 twist rate. So the military compromised on a 1x7 twist rate for the new ammo.

Shorter (which USUALLY means lighter) bullets can be fired in barrels with tighter twist rates than in necessary but longer (which USUALLY means heavier) bullets cannot be shot in barrel twist rates that are slower than what they need. So the most versatile barrel twist rate is one that is tighter as it will shoot all bullet lengths/weights.

An example of what happens when uses a longer/heavier bullet in a too slow twist rate is shooting a SS109/M855 62 grain bullet in a 1x12" twist barrel. What will happen is right around 100 meters the bullet has lost too many RPM's and will actually start flying end over end - with horrible accuracy. The bullet may strike "sideways" - which is called "key-holing" - leaving a sideways imprint of the bullet. Hitting a body with a "key-holing" bullet aint bad - the bad part is the bullet won't go where it was aimed - so you only hit with a "fluke". Since our goal is to hit when we are aiming at something - key-holing is BAD. MIssing is WAY TOO easy with bullets that fly true - missing is almost garaunteed with bullets that don't fly true.

Bushmaster which was really the first company to start building ARs in a big way looked at the available ammunition back in the 80s when they started and back then 62 grains was heavy for .223s. Well the 62 grain lead projectile only needs a 1x10 twist to stabilize and since some 68 and even 69 grain projectiles were on the horizon they figured what the heck lets have our barrels be 1x9 twist. No one is going to be shooting heavier/longer bullets than 69 grains so 1x9 twist will be fine. Remember back then most bullet weights/lengths were in the 40-55 grain area.

Bushmaster soon became the leader in ARs and when more and more companies came on board they followed the leader and had their twist rates be 1x9 also which UNTIL the heavier bullets came along just a few years ago worked out just fine.

Now advance forward to just a few years ago when the war on terror started in earnest. The 62 grain bullet wasnt cutting the mustard. Due to different manufacturing techniques of bullet manufacturers some lots of the M855 wont fragment they way some other lots of M855 will and we all know that if the bullet doesnt fragment it doesnt work as well as when it does fragment. Also the range at which it will fragment is less than 200 meters. Couple this with the fact that the M855 bullet since it has a lead and steel core can NEVER be as accurate as a bullet that has an all lead core making distant sniper type shots a lot harder.

So SpecOps units started looking for a different bullet. (This is what started the ill fated attempt of the 6.8 SPC.) The military match shooters at the time were dominating the shooting matches using bullets that were 75-77 grains in weight. These bullets would allow our boys to make shots out to 600-700 meters with confidence of a hit cause they are extremely accurate bullets. What the SpecOps boys found out that in addition to being accurate these heavy bullets FRAGMENTED when they hit most water based mediums (bodies). And they fragmented with much more vigor than the 62 or even the 55 grain bullets cause since they were heavier/longer they had more material to fragment with! AND they are fragmenting at ranges far in excess of 200 meters.

These heavier bullets are doing such a good job that the 6.8 has since died on the vine.

So if one is getting a new AR or just a new barrel for SHTF purposes it would be my advice to a 1x7 twist barrel. The 1x7 twist will allow you to shoot ALL 55 grain ammo, 62 grain ammo and the 75 or 77 grain ammo. What you wont be able to shoot is the thin jacketed 40 grain ammo but no one would use that for SHTF purposes anyway! In other words you lose NOTHING by going to the 1x7 twist barrel but you GAIN the versatility of being able to use ANY fighting bullet made for the 5.56 family of firearms. So my question would be WHY LIMIT YOURSELF?? You may not have any of the 75 or 77 grain ammo - but why close the door on EVER using it??

Think in these terms - more and more LE units are moving to these rounds - the whole US military is looking at these rounds (because of the great success the SpecOps community is having with these rounds) - so this ammo is only going to be more prevalent as time goes on. DONT GET A NEW BARREL/UPPER that cant shoot these new rounds or you may live to regret it!

If your barrel has a 1x12" twist - you are limited to 55 grain ammo.
If your barrel has a 1x9" twist - you can shoot either the 55 grain or 62 grain (actually up to 69 grains reliably)
If your barrel has a 1x7" twist - you can shoo the 55 grain, 62 grain, 75 and 77 grain - even all the way up to 80 grains reliably

As far as ammo choices:
First choice BY A LONG MARGIN would be the 75 or 77 grain ammo it fragments beautifully from point blank out to many hundred meters.

Second choice would be M193 or equivalent 55 grain ammo if fragments reliably from point blank to around 150 +/- meters.

DISTANT third choice would be the SS109/M855 62 grain ammo which is not a reliable fragmenting round at any range.

[Cokebottle]

What you wont be able to shoot is the thin jacketed 40 grain ammo but no one would use that for SHTF purposes anyway!

I disagree.

The most realistic SHTF scenario is going to be a natural disaster that forces us from our homes.
When you are bugged out, the two most important things are water and food. Everything else is secondary.

The majority of shooting during a SHTF situation is going to be hunting... and the deer, hogs, bear, and other large game are going to be extremely hard to find due to them moving away from the new human activity, and the rest will be hunted out within days or weeks.

What's that leave? Small game. 'Yotes, dogs, cats, etc.
You're going to be using 40gr if you want to have any meat left on the body you recover for dinner.