I keep seeing ads for entry level offerings from the typical online vendors, Palmetto & Bear Creek that typically have 1:7 twist barrels. I see that the overwhelming majority of ammunition, especially at the lower price point, in both .223 Remington and 5,56 NATO are usually 55 grain FMJ. Wouldn’t logic dictate a slower twist barrel for these light bullets? I have to look pretty hard at these websites to find barrels with 1:9 twist, so what’s up with that? Is it cheaper to manufacture a fast twist barrel?
AR-15 what’s the logic?
- Thread starter igotta40
- Start date
General Geoff
Member
1:7 stabilizes 55gr just fine, along with heavier bullets. Entry level rifles tend toward working "OK" with all types of available ammunition, rather than be tailor-built to take advantage of one specific bullet weight.
Shanvanvocht
Member
It's not the weight of the bullet, but the length that determines the required twist rate, although heavier weight equates to longer length in a given diameter. The original M16, firing the 55gr M193 round, had a 1:12 rate. That was changed to 1:7.3 to accommodate the 62gr M855and the longer M856 tracer round. Generally, 1:9 will stabilize most .223/5.56mm bullets up to 62gr, but many manufacturers use the faster rates (1:8 or even 1:7) to better stabilize heavier, and therefore longer match bullets up to 77gr.
General Geoff
Member
Ain't that the truth. The ever-increasing urban population bias means that most gun owners will never even visit a range with greater than 100 yard targets. I know my local range doesn't have anything beyond that, and to get beyond 200 I have to drive over 50 miles away. The nearest in-state 1,000 yard range is almost 150 miles away.
The M855 bullet will stabilize just fine with a 1:9 twist. It is the longer 64grain M856 tracer bullet that will not. The M856 being longer needs the 1:7 test to properly stabilize and also have the same trajectory as the M855.
@igotta40,
There are several reasons why the 1:7 twist is so popular. One reason is simply because that is what the US Military uses and civilians like to copy and use the same things. The other big reason is that 1:7 will stabilize such a wide range of bullet weights and lengths to include the very heavy for caliber bullets that are 75 grain and heavier.
MachIVshooter
Member
There's really no good reason to go slower twist than 1:7 unless you're handloading for long barrels that achieve blistering velocities with lighter bullets.
Some of mine are 1:7, some 1:8 and a couple 1:9. They all shoot the weights I use, 40-62 gr, just fine. The Varmint rig is a 22" bull barrel, which might have issues at 1:7, but it's a 1:8, and I've had no trouble with 40 gainers that are running 3,500 FPS.
Some of mine are 1:7, some 1:8 and a couple 1:9. They all shoot the weights I use, 40-62 gr, just fine. The Varmint rig is a 22" bull barrel, which might have issues at 1:7, but it's a 1:8, and I've had no trouble with 40 gainers that are running 3,500 FPS.
Ranger99
Member
I wouldn't mind having an AR or two,
but I'm not paying a grand for one
but I'm not paying a grand for one
MachIVshooter
Member
That has to do with bullet quality, not weight. Try some premium 55 gr varmint or target bullets.
I hear you. For a general purpose AR, I like a 1 in 8" twist barrel. Not a lot of those around, and when they do show up at PSA, they sell out in minutes. 1 in 9" is also pretty good for most bullets starting at Varmint weight up to 62 grain .
I suspect the 1 in 7" twist barrels are so common, because of machines set up for mass production, mainly for filling military contracts
I suspect the 1 in 7" twist barrels are so common, because of machines set up for mass production, mainly for filling military contracts
its exclusively marketing. "Milspec".... and all that. The government spent an absurd amount of money proving 1 in 9 works great.
But you need tracers for your infantry rifle right? Yea so 1 in 7.
Naturally 20 years later heavy for caliber bullets came out to make use of that.
Now its the trend for most calibers.
Go on AR15.com com and tell the world you bought a 50$ barrel in 1 in 9 twist that shoots 1/2 MOA and people will say you were ripped off.
I once heard a guy say "you should only buy an AR in 1 in 12, or 1 in 7. 1 in 9 is worthless". Not sure how that works. My guess is that he's an idiot.
But you need tracers for your infantry rifle right? Yea so 1 in 7.
Naturally 20 years later heavy for caliber bullets came out to make use of that.
Now its the trend for most calibers.
Go on AR15.com com and tell the world you bought a 50$ barrel in 1 in 9 twist that shoots 1/2 MOA and people will say you were ripped off.
I once heard a guy say "you should only buy an AR in 1 in 12, or 1 in 7. 1 in 9 is worthless". Not sure how that works. My guess is that he's an idiot.
Like @MachVshooter said that's just 55gr FMJ's doing their thing. They shoot mediocre from 1:9 too.
Try some Frontier 55gr HP match.
I have a 6" twist on one rifle and it shoots the light stuff just fine contrary to popular belief. It also will single load 88 eldm's and launch them pretty predictably at 1000 yards. I have yet to work on that 88 load but it looks promising. I like 8" for rifles and 7" for carbines as a general rule. If not 75-77 grain bullets will be shot than 9" is the best. There is no practical reason to shoot anything heavier than 62 grains unless you are trying to shoot longer ranges more accurately.
dh1633pm
Contributing Member
I have always used this chart to keep things straight:
Pat Riot
Contributing Member
Not trying to be a jerk but this would be quite a task before CoVid. Now? I don’t think so.
someguy2800
Member
For what I use my 223 AR for I prefer the 75 grain Hornady bthp or 77 grain sierra’s. All of mine are 1:8 twist. That is the ideal all around 223 bullet weight in my opinion
someguy2800
Member
Can get 2 of them for $1000 no problem. If you really bargain shopped for parts I think building three for $1000 is still probably doable, but it’s going to be bargain basement blem quality parts.
Yes faster twist rates prefer longer/heavier bullets. But I have also seen 1-8 and 1-7 twist barrels shoot 50-55 grain bullets very accurately. I can remember when it was way easier to find 1-9 twist barrels compared to 1-7 twist barrels. But everyone wants MIL-SPEC and/or have switched over to long/heavy bullets so now 1-7 and 1-8 twists are the norm.
I don't really notice much of a difference with 1-9, 1-8, and 1-7 twist barrels when shooting quality ammo at 300 yards and under. As with any firearm, one needs to find what each gun prefers and shoots the best.
I don't really notice much of a difference with 1-9, 1-8, and 1-7 twist barrels when shooting quality ammo at 300 yards and under. As with any firearm, one needs to find what each gun prefers and shoots the best.
CoalTrain49
Member
A 1:7 twist is not going to shoot 55 grn bullets very well, no matter how much money is spent on the rifle. The 1:9 barrel is best for stabilizing lighter and mid-weight bullets between 40 and 62 grains, which is what most people shoot in their AR. 1:7 twist is used by the military to stabilize 70-90 grn bullets.
I built a precision bolt rifle to shoot 55 and 62 grn bullets. I chose a 1:9 twist barrel.
I think the 1:7 twist barrel came about from the military M4 pattern. It's what the military uses.
I built a precision bolt rifle to shoot 55 and 62 grn bullets. I chose a 1:9 twist barrel.
I think the 1:7 twist barrel came about from the military M4 pattern. It's what the military uses.
Varminterror
Member
- Joined
- Jul 17, 2016
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1:9” twists used to be the standard for most civilian “entry level models,” of AR mil-spec-ish carbines. But consumers realized the limitations of the 1:9” twist, especially in the short 16” barrels, and when one competitor started selling 1:7” as standard, the simple phrase “well I was gonna buy Brand X, but Brand Y has a better twist, so I bought Brand Y” was a death knell for these 1:9” models.
The reality is simple. 1:9” barrels don’t actually shoot lighter bullets any better than 1:7” - especially in short 16” barrels - so consumers want versatility, whether they’ll ever make use of it or not.
So it’s not cheaper to make fast twist barrels, but it’s far, far easier to sell fast twist barrels than slow twist, and it’s a lot better for companies to sell products than not.
