I need some advice in what barrel twist I should buy, thank you

Well that all depends on what you intend to do with your rifle.  Varmit...match shoots...defensive purposes?  There is even an ideal barrel length for what your intentions are for the rifle.

1/7 will stabilize the heavier rounds.  These bullets are ideal for defense and barrels of shorter length.

1/9 will stabilize a larger range of bullet weights.  This twist is found more on full length rifles (20" bbl).  You will use this length more for distance shots.

Read the FAQ in the ammunition forum.  It will explain more in depth bbls, ammo, and twist.

It just depends on what you want to do with the rifle.

Wow, we haven't done this one in 24 hours...  See the links below for some good info on the barrel twist.

www.ar15.com/forums/topic.html?b=3&f=12&t=190881

www.ar15.com/forums/topic.html?b=3&f=12&t=197439&page=1

I decided to change all my rigs to 1/7 barrels, save a couple.  I almost exclusively shoot 69gr or 77gr SMKs, so I needed the 1/7 barrels.  Here are all of my non-1/9 setups either built or being built (as noted).

Mk12 Mod1 SPR clone - 18" 1/7 WOA barrel
RECCE carbine clone - 16" 1/7 Bushmaster HBAR
A4gery - 20" 1/7 Colt gov't profile
SAM-R clone (building now) - 20" 1/8 Bushmaster DCM barrel
M4gery - 14.5" 1/7 Colt gov't profile
Middy setup (waiting for giffman to finalize the 1/7 middy barrel group buy) - 16" 1/7 ????
Commando setup (can't decide if I should install a FF rail, which isn't really needed or just an RAS) - 11.5" 1/7 Bushmaster HBAR with 5.5" FH

Why did the FBI and DEA go to a 1/9 14.5 in that RRA contract if it was that big of a deal?  Is it that big of a deal if I'm shooting M193 or M855?  I havent found it to be, even though I am not shooting at 600m. (who really is?  I do that with my 7.62 M.25 clone).  If I'll never really be spending big bucks on 77 gr. Black Hills, etc., and only using 55 gr. and 62 gr. wouldn't the 1/9 be better?

Quoted: Why did the FBI and DEA go to a 1/9 14.5 in that RRA contract if it was that big of a deal?  Is it that big of a deal if I'm shooting M193 or M855?  I havent found it to be, even though I am not shooting at 600m. (who really is?  I do that with my 7.62 M.25 clone).  If I'll never really be spending big bucks on 77 gr. Black Hills, etc., and only using 55 gr. and 62 gr. wouldn't the 1/9 be better?

The military went to 1/7 to stabilize their tracers, IIRC.  My guess is that the FBI & DEA probably don't use tracers much and didn't see the need for the 1/7.  They are likley shooting some type of LEO ammo (like TAP), which doesn't have the need for a faster twist barrel.

With what you are shooting, there is little need for a 1/7 barrel.

What I have done, in my case, is expanded what I can shoot accurately and reliably.  I can still shoot 55gr and 62gr stuff in 1/7 barrels also.

Both will serve OK for 99% of us (exception being if you are shooting the long match bullets or tracer). Main reason people buy 1/7 is because they are anal about being as close to "MilSpec" as possible. Same deal with 4140 vs 4150 steel, F-marked FSB, M4 feedramps, Colt handguards etc. etc.. It all depends on how anal you are.

ANAL, ANAL, ANAL, ANAL, ANAL... love that word

All questions will be answered by the Ammo Oracle

Quoted: ANAL, ANAL, ANAL, ANAL, ANAL

I will admit I was guilty of the above accusation when I built my SPR and M4gery, but the accuracy and versatility of the 1/7 barrel prompted me to change all my rigs to 1/7 where possible.

Is the 1/7 more accurate with M193 and M855 than a 1/9?  I haven't found it to be so.  Then again, I'm not a Camp Perry champion.  Why would 1/9 become a default twist with commercial (non military tracer shooters) if it was not as good as  1/7?  Is it cheaper to manufacture a rifle with a 1/9?   A 1/7 puts more spin on a bullet, but is that more spin a good thing at stabilizing it up to 300m?  How many people here really shoot things out past 300m with a .223?  I'm thinking anal too, but only because I am anal, which is why I'm asking these questions.  That Ammo Oracle is good stuff btw.

Quoted: 1the VAST MAJORITY of people shoot bullets between 55-69gr in ARs -Troy

Likely because there is abundance of relatively high quality, inexpensive surplus ammo in 55gr and 62gr.  I chose to go the 69gr and 77gr for the reasons Troy mentioned - longer effective range and good defensive potential.

Therefore, I am an ANAL, but happy 1/7 barrel user.

1/9 is the most versatile . Ammo is plentifull and cheap...............and it will shoot any bullet that the 1/7 will shoot . ........and in my experiences will sale a little sooner than a 1/7 .

One thing I think others failed to mention is that the 1:7 twist will wear out a barrel quicker than a higher twist rate, around 50,000 rounds if memory serves correctly. No biggie in my opinion, but something to consider if you burn a lot of ammo.

Kevin

Mongo, it's ok to be anal as long as you aren't washing your hands every 15 minutes or driving back home three times a day to make sure your doors are locked.  Then again, I do have the cleanest hands in town, and the house most likely to have its doors locked.  Excuse me while I go wash my hands.

Quoted: 1:9 is default because the VAST MAJORITY of people shoot bullets between 55-69gr in ARs, and this range is ideal for 1:9.  However, in the last few years, it's been discovered that heavier match bullets are very good for defensive/combat/duty use, with excellent terminal ballistics, but these need a faster twist to work reliably.  Thus the recent trend back to 1:7 barrels for duty guns. If you don't plan on using the 75-77gr ammo, then you absolutely don't need a 1:7 barrel.  Due to the high cost of the ammo, most people won't be using 75-77gr ammo, so 1:9 barrels are just fine.  If you're one of the exceptions, then look into 1:7 options. -Troy

That's all true enough sure, but the 1/7 seems to handle the 55gr as well as the 1/9, I don't see many people using lighter than 55.  So, with 55gr, either is fine, with 69+ gr, 1/7 is better.
So, if it doesn't cost more, I think the 1/7 is better for most folks. :)

As an example, folks have tried to tell me my Colt 6400C's 1/7 barrel isn't going to work as good as a 1/9, which I don't find.

What someone needs to do is take two 14.5 uppers, a Bushmaster 1/9 and 1/7, same lower (trigger pull) and run several types of M193, M855, and some heavy bullets at say, 100 and 300, same day, same conditions, and see whats what.  I don't think barrel life means squat when we're talking the difference between a 30,000 and 25,000 rd. life.   I also don't think twise means squat when we are talking about virtually no diffference at 300 yds.  I know this may be flawed due to barrel difference, but it's a start.  BTW, do you really want a .223 bullet super stabilized (i.e., an ice pick hole) or do you want it stable until it hits some meat, then it yaws and tumbles?  What was the "trouble" or issues the military had with 1/7 that I read about?

If you really want a round that tumbles on impact, I believe the way to go would be with the original 1:14 (?) twist in the early M16's. The VC and NVA were apparently "impressed" with the damage done from these rifles using the standard 55 gr. nato round. Unfortunately, the military soon changed over to the 1:12 twist to stabilize the rounds.

Kevin

Quoted: If you really want a round that tumbles on impact, I believe the way to go would be with the original 1:14 (?) twist in the early M16's. The VC and NVA were apparently "impressed" with the damage done from these rifles using the standard 55 gr. nato round. Unfortunately, the military soon changed over to the 1:12 twist to stabilize the rounds. Kevin

You both need to read the Ammo Oracleammo-oracle.com/

It will get you straightened out fast.  There is no such thing as a super stabilized bullet and the 1-14 twist was marginal for even M193.  So accuracy sucked.


Read the Ammo Oracle!

I want it all.  I want it to be stable until it hits the target and penetrates a bit, then tumble.  I believe the problems, if prevalent, with the 1/7 M855 is that it is stable through and through, like an ice pick wound.  The big selling point of the .223 is that it yaws and does bad things in flesh.  Isn't this the big thing with the big long 75 gr. plus bullets?  Frankly, this is mostly conjecture for us armchair commandos anyway as if I get into it, it is going to be with my .45 auto, 230 gr. jhp's.  Even better, my Beretta Silver Mallard synthetic and a couple 00, or 000, or even #4.  A couple of those (or even one) in the thorax is likely going to drop the goblin quicker than .223's.

Quoted: If you really want a round that tumbles on impact, I believe the way to go would be with the original 1:14 (?) twist in the early M16's. The VC and NVA were apparently "impressed" with the damage done from these rifles using the standard 55 gr. nato round. Unfortunately, the military soon changed over to the 1:12 twist to stabilize the rounds. Kevin

123 Whisper you are right about the 1:14 twist being more inaccurate than the 1:12 and I should've stated that in my post (kinda did in a roundabout way). I have only shot one AR15 with the 1:14 twist and it was at short range, 100 yards. I did not notice any difference in accuracy from the M16A1's and other AR15 SP1's on the firing line that day. However, we were not shooting for groups (exactly what we where shooting at is classified information). Anyway, I am pretty sure about the tumbling effect from that twist rate as it has been documented in the M16/AR15 literature. Will check out the website you recommended anyway.

Just printed and then read most of the Ammo-Oracle - although much of it is basic knowledge to students of the AR15/M16 weapon systems, it is a excellent paper and I highly recommend it. Maybe the 1:14 tumbling effect is myth, but would still like to see any data the military may have collected on human tissue. THe gellatin studies could have probably been left out as I remember others using such to justify the 9mm round over the 45 acp in stopping power. Hogwash as we know. Maybe if we are ever attacked by jello monsters from outer space we should all arm ourselves with 9mm's (been said before and deserves repeating in my opinion), but until then I'll stick with with the 45, gellatin blocks be damned    

Kevin

i like 1 to 8... i feel that 1x7 doesn't do what I want of it at lighter bullet weights...  

i picked 1x9 for my barrel though... i wanted it to last longer so i picked a slower twist... 68gr is good enough for me..  

i am heading out to the range to see how 75 works... i'll keep everyone posted....

Quoted: i like 1 to 8... i feel that 1x7 doesn't do what I want of it at lighter bullet weights...   i picked 1x9 for my barrel though... i wanted it to last longer so i picked a slower twist... 68gr is good enough for me..   i am heading out to the range to see how 75 works... i'll keep everyone posted....

If someone starts making a M4 profile 4150 barrel that's fully chrome lined I will definitely get one.  Until then I'll stick to the 1/7.

BTW, our very own Brouhaha has used 40 grain bullets with good results from a 1/7, see the first link I posted above.  How much lighter do you want to go?  

I also think the barrel life issue is exaggerated, unless you do mostly full auto shooting and even then I don't think there would a big difference either.

Like many others I also noticed no accuracy degradation between my 1/9 and 1/7 uppers.  My 1/7 loves XM193 and shoots it very well when I do my part.

There is so much contradictory data floating around that I wonder if the whole issue is BS.

bigbore takes a 16", 1/9 carbine to the 600yd range and it performs well using 77gr SMKs.

Brouhaha takes a 1/7 barrel and shoots 40gr bullets without any problems.

I was always under the impression that barrel life would be dramatically shortened by shooting super-fast bullets through the barrel, but I never heard of twist affecting barrel life until I read it on these forums.  I don't know exactly how I feel about it, but my gut says that there is likely little difference between the life of a 1/7 & 1/9 chrome lined barrel.

Regardless, I saw immediate, positive results in accuracy when I switched to 1/7 barrels and 69gr/77gr SMKs.  Was it the improvement of equipment and bullets that made the difference or did the whole outfit better suit the way I shoot.  Who knows.  I never shot a 1/2" or less group before.  Now I do on a pretty regular basis.

I felt obligated to include the wear factor in my previous post ; but didn't !   ....also  I feel strongly that an AK is KING of CQC. Those of you that know ........... know what I mean . EXCUSE ME  got off the subject.....anyway the 1/12  with 55g has a scientific aspect that should not be tampered with outside of special application  it produces results unless initial penetration is a factor.  1/9 and 55g is the meat and taters fellas ! The only reason I would consider a 1/7  -  62g  is to mimic the penetration factor of the service ; but they are loosing the tumbling and relying more so on the 3 shot burst coupled with the 62g 'penetrator' . These are all specific applications for specific jobs  ..... The AR system is versatile and modular and can be adapted ...........boils down to "we still want 1 gun to do it all and the AR comes close !!!"      HAMMER

Quoted: I never shot a 1/2" or less group before.  Now I do on a pretty regular basis. www.hunt101.com/img/193578.JPG

The only problem is, you missed!

Quoted: There is so much contradictory data floating around that I wonder if the whole issue is BS. bigbore takes a 16", 1/9 carbine to the 600yd range and it performs well using 77gr SMKs. Brouhaha takes a 1/7 barrel and shoots 40gr bullets without any problems. I was always under the impression that barrel life would be dramatically shortened by shooting super-fast bullets through the barrel, but I never heard of twist affecting barrel life until I read it on these forums.  I don't know exactly how I feel about it, but my gut says that there is likely little difference between the life of a 1/7 & 1/9 chrome lined barrel. Regardless, I saw immediate, positive results in accuracy when I switched to 1/7 barrels and 69gr/77gr SMKs.  Was it the improvement of equipment and bullets that made the difference or did the whole outfit better suit the way I shoot.  Who knows.  I never shot a 1/2" or less group before.  Now I do on a pretty regular basis. www.hunt101.com/img/193578.JPG

I wouldn't say it's BS since there may be variances in barrel manufacturing, shooter skill and even ammo loading especiallly if you reload.

As for my personal goals and requiremnts the 1/7 is more versatile because it will shoot 40gr on up to 100gr.  Of course there will be issues with the lighter thinly jacketed bullets but I'll gladly give those up for the terminal performance of the heavier bullets and knowing "for sure"  that my barrel will shoot them with good accuracy.

Will some 1/9 barrels shoot the heavier loads?  Maybe, maybe not but you can decide if you want to take that gamble.  In my case my 1/9 shot patterns with the Blackhills 77gr, maybe yours will do better.

Again what it boils down to is what YOU want to be able to do with your carbine/rifle.  Decide what you want and pick the right twist for the job and damn what anyone else thinks...

I also want to add that stability in flight has no correlation to stability in flesh.  The whole idea of bullets firing from 1/7 causing ice pick wounds due to over stabilization is pure BS.  It's was more likely the bullet struck at a distance where the velocity was not high enough to cause it to yaw and fragment.  The whole 1/12 twist and tumbling bullets is a proven myth, get over it already.  The terminal performance of 5.56 bullets is all about velocity and bullet construction.  As mentioned before READ the AmmoOracle FAQ and Dr. Fackler's papers pinned on the Ammo Forum!

Quoted: Quoted: I never shot a 1/2" or less group before.  Now I do on a pretty regular basis. www.hunt101.com/img/193578.JPG The only problem is, you missed!

LOL! I was going to say that too but I didn't have the heart...

Quoted: Quoted: Quoted: I never shot a 1/2" or less group before.  Now I do on a pretty regular basis. www.hunt101.com/img/193578.JPG The only problem is, you missed! LOL! I was going to say that too but I didn't have the heart...

I need to explain myself for those who don't understand load work-up.  I don't immediately zero my scope for each load.  So during load work-up you will ALWAYS see my POI different then my POA.  I don't zero until I have found the load I like, then I zero.

Correct in the fact that I missed the orange dot, but I wouldn't have missed YOU (whoever "YOU" are)!

OK, I expect incoming, but here it is:  The 5.56 / .223 is not a cartridge I would pick to do anything but punch holes in paper out past 300 yds.  That is an extreme combat distance anyway, so the .223 is fine for it.  Most military sniper kills are within that distance.  If you've ever fired in high power matches and/or DCM matches, you know that is a long way to be attempting to hit a torso without 4x magnification.  Add that the torso is moving, using cover, and not standing upright while a pattern is grouped, and that someone else is trying to shoot your torso and we understand that 300 + yd. shots are rare.  Out past 300 yds, I want the 7.62x51 (NOT an AK round).  It bucks wind, punches through cover and armor, and has plenty energy and size left.  Of course it has been supplanted in service matches because a souped up .223 doesn't kick, no cover or armor needs to be busted, no knockdown is needed, just  snap and a tiny hole appears in a thin paper target.  If jellymen from space or brain eating zombies attacked, or riots and chaos broke out in my community, I'd snatch up one of my M4 clones with the Eotech 552 or Combat Elite IR (sorry, I haven't found the need to replace it with a $1000 ACOG as it works just fine, is rugged as a tank AND has BAC !).  The upper I would snatch would not have any bearing as to 1/7 or 1/9 (as all perform about the same, close to moa), it would have to do with what was on top and zeroed.  If the space gummi people or zombies were really scary, fast, and returned fire, I'd find a hide, cover myself with a skeeter net, dirt, grass, etc., and do my work from 300+ with my M25 clone and Leupold M3.  Then, I'd didi off to hide.  But is any of this going to happen.  Nope.  What I should do is get off my lazy a$$, go out to the 100/300 yd range, and fire both my Bushmaster 14.5 1/7 and 1/9 for comparison with 55gr. and 62gr. and report back here.  My problem is that I doubt I would be able to perceive (I havent yet) or report much difference that wasn't due to shooter inadequacy.  BTW, I do know how to shoot, and am a "pretty good shot", but even rested, sandbagged, etc., 1/4 to 1/2 moa may be anything from a heartbeat, triggerpull, gust of wind, barrel idiosyncracy, etc.

mongo001,

LOL

No need to explain yourself I do the same thing when testing different ammo types.  We're just yanking your chain...

Quoted: mongo001, LOL No need to explain yourself I do the same thing when testing different ammo types.  We're just yanking your chain...

I know most here do, but there are alot of newb's that may think that I am a 'tard for bragging about that group and not actually hitting the target.  As a matter of fact, when I first posted that group, that exact question came up.

Quoted: Again what it boils down to is what YOU want to be able to do with your carbine/rifle.  Decide what you want and pick the right twist for the job and damn what anyone else thinks...

I don't really think many people present 1/9 as better than 1/7. Most of these threads seem to have the approach that "1/9 will do you just fine", which to me says "1/7 is better, but 1/9 will do fine." I don't see any reason folks would pick the 1/9 over the 1/7, unless they're shooting lots of light ammo, and then you're probably better off with 1/12 or something. :)

(most 223 bolt guns are 1/12 or 1/11, I think they make an LTR in 1.7, but anyone know of a cheaper 223 in 1/7?)

I think the Ammo Oracle's formula indicates that a 1/9 is better (given the formula used to determine such things) for 55 gr. and 62 gr.  The 1/7 came first, after the 1/12, to stabilize the longer M856 tracer.  For accuracy and barrel longevity (which is not really an issue to most of us) the 1/9 is supposed to be better for those rounds, hence the reason that commercial and LEO rifles use it and Colt went to it.  No reason for Colt to go to a 1/9 when they are all tooled up to 1/7 unless they had/have a reason.   The 1/7, per the Oracle, may overstabilize the 55-62 gr., hence it isn't as accurate.  Colt, Bushmaster, etc., obviously have a reason for going to the 1/9 as a default twist as it seems to me that it would have been easier to use existing equipment and running one line, as to a separate one for 1/9.