I have been lurking for a few months and trying to pick up as much as I can before I start asking the inevitable stupid noob questions. That being said, here goes:
I am going to be purchasing my first AR next month. I have decided to go with an adjustable piston system(just my pref. though it may be based on an ignorant bias). in 5.56. I have set a $ limit of $1,600.00 without any extras.(though this number somewhat flexible). I would love to build from the ground up but just do not have the time available to do it right. My problem is that every time I find a complete rifle that has the features that I want in my price range it invariably has a 1/9 twist.
I have searched for info concerning the advantage/disadvantage of 1/9" twist rate. I find that all agree that 1/7 or 1/8 to be better for the longer/heavier rounds. I understand the reason for this and do not argue it.
How big is the disadvantage of 1/9 with the longer rounds? Is the real issue simply one of long range accuracy or are there real safety issues? Is there any disadvantage to running 55gr in a 1/7? I know that this info has to have been covered here but I am just not finding it. A nudge toward the right thread …?
I am willing to spend a little extra if need be but I don’t want to spend more if it only means being able to hold sub MOA groups at 300yds. I will not likely have the opportunity to test this anyway. I will be shooting mostly 55gr as this the most affordable for me and I am limited to 100yd range. This is primarily going to a recreational range toy.
The primary issue is accuracy. With a 1/7 using 55gr. you won’t have any real issues and as most people will tell you, you can still hit targets out to at least 200M with ease. One thing to consider is that most 1/7 barrels from known reputable dealers are going to be HP/ MPI tested whereas to the best of my knowledge most 1/9 barrels will not.
At the price point that you are shopping getting 1/7 isn’t going to be much of an issue as you will find it to be pretty much a standard feature for that money.
IZGUNS brings up an important point. Typically speaking, barrels with a 1/9 twist have a much higher chance of being over gased, rifle barrel extensions, cheaper steel and some .223 hybrid chamber (even though it says 5.56 NATO on the barrel).
It has been my experience most AR shooting is done at short range “carbine” distance- under 300 meters and the vast majority under 150 meters. In those distances the 55 to 62 grain bullets in a 1-9 twist are more than sufficient. the use of heavier bullets at ranges beyond 300 may start to show an advantage to the 1-7 so honestly ask yourself what niche you are filling with an ar. If you plan on doing a MAJORITY of your shooting beyond 300, perhaps you should get a 308
I have shot many thousands of rounds through 1/9 barrels for 2 main reasons.
They were reasonable in cost at the time. The prices on guns/uppers/barrels in 1/7 has come down significantly since I bought all those 1/9 barrels.
All I shot was 55gr. 55gr has no issues out of 1/9 and since that’s all that was going down the barrel, 1/7 offered no advantage for me. I now have a variety of ammunition at my disposal, and I’ve seen how 1/9 reacts to some heavier (read: longer) bullets and I need better performance than that.
In a nutshell, that’s why I’m switching from 1/9 to 1/7. I wouldn’t call 1/9 a deal breaker, but I would say that anything I have that is 1/9 is limited to 55 gr ammo only.
I am not dogpiling on you, but I do have a serious question. Why would you not want to use a heavier bullet when stopping the threat as quickly as possible is what we are after?
It’s been well proven that in addition to shot placement, the heavier rounds are proving to be better stoppers in the carbines.
As Tood mentioned I can kill you with a .22, but why when all you have to do is have the right barrel and ammo?
I guess this really boils my long winded question down the best.
I will be shooting mostly 55gr
I would like to be able to shoot heavier for HD/SD
How unstable/inaccurate would the 1/9 be with 70+gr rounds?
You would want to use a heavier bullet, but in response to the question “Is 1/9 a deal breaker” I’m surprised that:
The answer could be yes.
The reason it’s a deal breaker is close range lethality over it’s effects on target at range.
If given a choice, I’d still buy a 1/7, but 1/9 is by no means a “deal breaker.”
The OP:
Quotes his budget at $1,600- no issue w/ purchasing 1/7 or 1/9 there.
Will primarily be feeding 55 gr due to ammunition cost- optimal twist calls for 1/9.
Primary use is recreation- accuracy w/ desired bullet weight trumps lethality.
We can enter a discussion of why 22 grains enhances the lethality, (it does) but this can be offset by the use of TAP or other engineered rounds, and matters less than shot placement when it comes to neutralization.
Please don’t kill me, I only disagree with your advice based on the above.
I would go 1-7 purely for versatility and rethink the piston AR thing, all a piston does is add uneeded weight and other issues as they only really shine in SBRs, get a BCM or Noveske. My BCM came to around 1400 tax tag and title and shoots 55gr every bit as good as 77gr.
I love my Noveske 1x7 CL - it shoots excellent groups with heavy bullets, but pretty much sucks with 55gr IMI M193. My BM 1/9 shoots the light stuff much better. Sample of one and all that.
My 1/7 shoots BH 52gr Match better than anything I’ve tried to shoot groups with. Shooting 55gr in a 1/7 twist does not concern me in the least.
There are loads that will work in the 1/9 that perform well for HD. Some are more difficult to find and more expensive so make sure you can get them where you are at or can afford to order a quantity online.
It’s not a matter of how accurate it will be at range but that those heavy bullets can tumble out of a 1/9 twist.
One other thing to note is,that some of the manufacturers advertising their barrels as 1/9 are sometimes actually not.
For instance my 2007 model Armalite 20" M15A4 SPR uppers with CM chrome lined barrels rod out to be right at 1/8 and as a result shoot heavy bullets rather well at distance.
Armalite claims the reason the barrels actually shoot the heavier ball well is because they double lap the bores…I say its because the twist is actually closer to 1/8.
So when you see folks say that their 1/9 twist barrel will stabilize heavy bullets at distance it may be the fact that they dont actually have a 1/9 and the only way to be sure is to rod the barrel to see what they have.
That said I think the days of the 1/9 are about to sunset with the majority of Ar manufacturers.The 1/7 and 1/8 are showing up more and more with the lower tier manufacturers due to market demand and loss of sales for not using what is preferred by their customers.
Same could be said about the 4140 steel.Armalites recent change to CMV is a good example that I never thought would happen.They have also recently commented that they are considering a switch to the 1/7 twist for the M15 CMV chrome lined barrels if demand continues in the direction it has.
So unless you want to spend your money on the older commercial driven 1/9 twist 4140 barrel and have a non-current assembly in the very near future,I’d buy what is recommended by the Industry Professionals here.
That said Iraggunz,Todd and Grant are not blowing smoke,they are actually trying to insure that folks get the most current and effective equipement.Considering the sources I’d take their advice as gospel.
It wouldn’t be a deal breaker for me, but I don’t see any reason why it would have to be. Of all the 5.56 carbines I might be interested in I can’t think of a single one that comes in 1:9.
While I would prefer 1:7 in all cases, and see no reason for the 1:9, if I was a cop and was issued a 1:9 I’d deal with it and choose ammo accordingly.
The more important thing here is you do not need a piston system for this gun especially since this is your first AR15. If you continue down this path, you will be looked down on by anyone that matters and be thought of as a wanabe in serious circles.
They have dubious benefits especially in a carbine length gun.
The only time they might be beneficial is if you are
Using a short length gun 10~11"
Using a silencer
Heavy amounts of rapid fire, like 1000 rounds a day heavy fire
If you cannot answer yes to atleast 2 from this list, you do not need a piston.
I suppose you are either looking at the S&W or Ruger piston offering since you said your budget was $1600, both of which have substandard quality over a Colt, Noveske, or BCM rifle.
A piston also brings a number of negatives into play such as more weight, more complicated moving parts, proprietary parts, and a decline in accuracy.
Alright guys here’s another question to bring up with the different twist rates…Is there any substantial difference in the round tumbling when it hits soft tissue? In theory the 1/9 would be a better candidate for this because it is less stable if using the same weight bullet in both ‘twists’ of barrels. If I recall correctly the original m16 came with a 1/12 twist and when the initial end users in Vietnam (army SF) returned to the states they recounted excellent results that were directly related to the instability of the round. As the military has gradually fastened the twist rate the reports of so called stopping power has decreased at the same rate. Granted most of us do not have to abide by the ridiculous Hague accord that mandates nonexpanding rounds. Would love to hear your feedback fellas.
