- May 29, 2017
- 7,770
Ruger AR15 uses 1:8
SW M&P Sport II uses 1:9
Colt uses 1:7
Is 1:9 cheaper barrel cheaper to make than 1:8 or 1:7
Why does different AR15 makers offer different twist rate?
- Thread starter Michigander08
- Start date
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Ruger AR15 uses 1:8
SW M&P Sport II uses 1:9
Colt uses 1:7
Is 1:9 cheaper barrel cheaper to make than 1:8 or 1:7
Longer (typically heavier in grain weight in practice as well) bullets typically require a faster twist rate to stabilize. What twist you want depends on what bullets you want to shoot.
Colt uses 1:7 due to military contracts as it's needed to stabilize the NATO tracer round. Colt does 1:8 or 1:9 in some commercial lines. Other makers will use what they believe gives the best compromise across the board for bullet weights. It could also be a cost compromise...which rate of twist is least expensive to produce.
- May 29, 2017
- 7,770
Yes. I understand that per chart picture. Twist rate on the side and bullet weight on top. I'm just curious why Ruger uses 1:8 and SW uses 1:9. It is because they think that what people want or because of cost in manufacturing.
Back when I was stupid, I sold an otherwise-decent upper because it had a 1:9 twist barrel. A bunch of idiots convinced me that I just needed a 1:7 because... I don't even know. I wasn't shooting a bunch of 77gr or anything. It just wasn't cool-guy enough.
These days, if you give me a good price on a high quality barrel that just happens to be 1:9, I'll jump on that fast. I shoot 55gr almost exclusively, so why wouldn't I want a 1:9? All things equal, yeah, I'd prefer 1:8, but if people are going to give me a big discount just because it's 1:9... I'll take it.
ETA: some people confuse the problems with 40gr bullets exploding from being spun too fast with the real issue caused by running 55gr in 1:7 guns - namely that you're spinning the bullet so fast that it suffers deformation and has a decrease in raw accuracy.
These days, if you give me a good price on a high quality barrel that just happens to be 1:9, I'll jump on that fast. I shoot 55gr almost exclusively, so why wouldn't I want a 1:9? All things equal, yeah, I'd prefer 1:8, but if people are going to give me a big discount just because it's 1:9... I'll take it.
ETA: some people confuse the problems with 40gr bullets exploding from being spun too fast with the real issue caused by running 55gr in 1:7 guns - namely that you're spinning the bullet so fast that it suffers deformation and has a decrease in raw accuracy.
Quite a series of leaps from Stoner's original 14 twist.
I can tell you from experience that the early pencil barrels with that twist weren't tack drivers.
alucard0822
For great Justice
Muzzle velocity is also a consideration. Heavier/longer bullets need a higher RPM to stabilize, but they have a lower velocity, especially out of short barrels. Bullet shape also matters, a flat base with a fat ogive will be a lot shorter, and take a slower twist than a sleeker boat tail of the same weight. I've found 69gr SMKs are on the edge of stability in 1:9 twist barrels under 20" and 55gr FMJBTs are plenty accurate from most all of my 1:7s, especially the 10.5". If you calculate actual RPM, the difference between the RPM imparted by a 1:7 vs 1:8 is usually about the same as the RPM difference between a 10.5" and a 14.5" barrel with the same twist once the velocity loss is factored in.
Boats
Broken Member
part of it is probably that (afaik, if someone knows different please speak up) neither Ruger nor Smith make their own AR barrels. It is cheaper. for them to sub contract AR barrels out to someone else. The supplier provides a barrel to their spec.
twist rate does not affect price of manufacturing, significantly.
The biggest part of why they use the twist they do is what they believe the customer wants. They are in the business of making and selling guns, after all.
I can tell you from experience that the early pencil barrels with that twist weren't tack drivers.
Never shot a 14, though they claim they were never meant for other than 40-52 grain.
Probably more than a little truth to this. Long for caliber bullets became a trend, and not only in .223/.556. Some is progress I suppose. Some might be arguably called little more than confusion.
Mr.Blue
Living In A Bizarro World
I’m not saying 1:7 is the best, but almost all the top AR manufacturers put 1:7 barrels on their rifles.
Many self defense shooters prefer the 77gr bullets for their better “knockdown power”, so would thus prefer 1:7.
I’ve personally found that high quality 55gr ammo does fine in 1:7 (usually in the 1-2MOA range).
Many self defense shooters prefer the 77gr bullets for their better “knockdown power”, so would thus prefer 1:7.
I’ve personally found that high quality 55gr ammo does fine in 1:7 (usually in the 1-2MOA range).
I wonder how many 7 twist barrels have never seen/maybe never will see a round longer/ heavier than the comparatively inexpensive (in normal times) 55 or 62 grain offerings that most people buy.
Yup
Me, too. I have never shot heavier than 62 grain. My .223/5.56 ARs vary from 1:7-1:8. All 16”
Me, too. I have never shot heavier than 62 grain. My .223/5.56 ARs vary from 1:7-1:8. All 16”
Keep in mind that the twist rate won't be a major effect on bullet stabilization until you get out to shooting at medium to longer ranges. I've had 1:12 and 1:7 barrels in the past and never noticed any difference at 50 to 100 yards. At 250 yards or more I think it may become a real issue. Maybe one of the guys who shoots competition and has more experience will address this better.
True. 1 in 12 to 1 in 16 are varmint gun twist for lighter .222-.224 bullets. Rifles chambered for calibers such as .222 Remington, .223 Remington, .22-250 used these twists with 40 - 52 gn bullets.
- May 13, 2005
- 2,780
My uncle has a Rem700 in 223, 24", with a 1/12 twist. Its favorite round by far is the 40g varieties. Although try and shoot anything past 62g and it will group them at about 12" at 50 yrds.
And this was pretty well standard for a lot of years, though the AR platform has had its own set of realities, and distinct from bolt guns. Differing twists, barrel lengths and precision expectations are primarily what comes to mind with the AR.
Lots of bullet crossover nowadays too. More than ever I think. Think of a 55 grain bullet at 3100, and you think .223. Push that bullet to 3800, and 22-250 or .220 Swift come to mind. Want 80-100 grain or thereabouts? Now think a jump to 24 caliber, typically in a 10 twist. But 24 caliber today can also mean 55 grain .243 diameter bullets, being pushed at 22-250 and Swift velocities. They are surprisingly precise too. On the other end of the 6mm/.243 spectrum is 115 grain. Used to think topping out at 95-100. That's quite a range of bullet weights. Some now heavier. Some now lighter. Same deal with the 6.5's and the 30's. Just a lot more variation in bullet weights by caliber today. Not a bad thing, but definitely different.
jimbobborg
Oddball caliber fan
I seem to remember back in the day that the better quality manufacturers used faster twist rates versus the cheaper guys. If all you're shooting is 55gr blasting ammunition, the 9 twist is sufficient.
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