1/7 or 1/9 Twist?

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Archangel14

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Gents:

I plan on building an AR with a 20 inch upper. I typically shoot 55 to 62 grain rounds. I would think that the 1/9 barrel would be a better choice. I'm lookin at a Stag 1/9 and a BCM in 1/7. Let's put aside the "quality of the manufacturer" arguments and focus on the twist rates. Your opinions?
 
Doesn't matter for typical ball ammo. If you intend to shoot the M856 tracer or 75 grain and heavier bullets, go 1/7 or 1/8. Conversely, if you plan to shoot 50 gr. & lighter varmint bullets, go with 1/9
 
I've shot a good bit of 55- and 62-grain loads through both 1/7 and 1/9 barrels. I could never tell one bit of difference.
 
Archangel14 said:
Gents:

I plan on building an AR with a 20 inch upper. I typically shoot 55 to 62 grain rounds. I would think that the 1/9 barrel would be a better choice. I'm lookin at a Stag 1/9 and a BCM in 1/7. Let's put aside the "quality of the manufacturer" arguments and focus on the twist rates. Your opinions?
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While some seem to do fine with light bullets and a 1:7 twist that has not been the case for me always. I would go with the 1:9 which I see as giving you more latitude. With my one Colt Sporter Target 1:7 using Nosler 55 grain ballistic tip boat tails I can get consistent 100 yard groups of keyholes. That at about 3100 FPS. :)
Anyway, for what you mention I would choose the 1:9 twist.

Ron
 
I also prefer the versatility of the 1:9, and wish it was as commonly used as the 1:7 is. I'm highly unlikely to ever buy and shoot the heaviest bullets that need the faster 1:7 twist.
 
While it probably doesn't matter, the 7 twist will handle lighter bullets better than the 9 twist will handle heavies. Unless you're going to be shooting a lot of 40 gr bullets, there isn't any real downside to going with the 7 twist.
 
My department uses a lot of Colts and exclusively 55 grn ball and hollow points. I have literally seen probably 10s of thousands of rounds of 55 grain ball through the 1in7 Colt barrels. They shoot it plenty accurate and Ive never seen or heard of anyone having keyhole problems.

It is true though that every barrel is different. Some 1in7 wont shoot 55grn and some 1in9 will shoot 75grn fine. But to say that 1in7 as a general rule doesnt do well with 55 grn ammo is just plain wrong. I would be surprised if a decent 1in7 barrel doesnt shoot 55grn ball accurately.

Personally I would buy the 1in7. It shoots the common plinking weight ammo well and if you ever decide to go with a longer bullet you wont have to worry about problems.
 
I shoot 60 gr. out of a 22" 223 rem barrel 1:12 twist. 1:9 is plenty tight for the bullets you listed.
 
jmr40 said:
While it probably doesn't matter, the 7 twist will handle lighter bullets better than the 9 twist will handle heavies. Unless you're going to be shooting a lot of 40 gr bullets, there isn't any real downside to going with the 7 twist.
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Sums up my thoughts as well.
 
First reply was spot on. To expand some on the subject you would have to test a large group of barrels to personally see that fast twist such as 1/7 is slightly more accurate than 1/9 with lighter bullets such as 55 gr not to mention the generous chambers on these ar platforms unless going custom chamber. Without looking it up even 1/9 twist is to fast for 55gr bullets however it seems it has become standard 223 rem twist across bolt action, ar, and others as well. If it were my decision I would pick the rifle I wanted based on whatever comparisons they are the 1/7 or 1/9 twist comparison with light bullet ammo would be near last or not even on my list.

I purchased a Bushmaster Varmint in 223 it would shoot winchester 40gr white box 40 round varmint pack from walmart .25" at 100 yards 10 shot groups... 1/8 twist
 
MIL-DOT said:
I also prefer the versatility of the 1:9, and wish it was as commonly used as the 1:7 is. I'm highly unlikely to ever buy and shoot the heaviest bullets that need the faster 1:7 twist.
Click to expand...
You shoot a lot of 40 grain bullets? 1/7 clearly wins the versatility argument unless you have a dedicated varmint rig. Most modern .223/5.56 ammo is 55 grain and up which the 1/7 handles well. Budget 77 grain stuff is likely around the corner. Plus the non lead stuff tends to be longer. Bottom line. Shooting long bullets well is more of a plus than shooting short bullets well in the AR world.
 
I am here to say with 55 gr bullets in a 1:7 twist there is a noticeable degradation in accuracy vs. 62 gr. Irritatingly noticeable.

I'm going to find a 1:9 upper to shoot cheap 55gr.
 
I shoot cheap ammo and dont reload. 1/8 or 1/9 is ideal for my purposes. I've never shot a .223 bullet heavier than 62gr. Myself, I prefer lighter Federal 50gr hp's for 'yotes. Laser accurate out to 300y and flat shooting.
 
1:8 twist is the way to go. http://www.gmriflebarrel.com/gm-m16-m16a2-5-56mm-20-barrel-with-extension-1-8-twist/

I personally don't see the advantage of getting a 1:9 twist for the sake of shooting cheap ammo a little tighter when it doesn't have great accuracy potential to begin with. OTOH I have 1:7 and 1:8 barrels that shoot 52gr OTM bullets as good as anything, and also shoot 75-77gr bullets which not every 1:9 barrel will do. \

I think 1:9 is better when you want to start going below 52gr in bullet weight.
 
How far out do you need or want to reach out and touch someone? While improved 200+ yard accuracy is theoretically nice, 98% or more of my shooting (with any caliber firearm) is at no more than 200 yards -- the heavier bullets and twist rates faster than 1/9" aren't really necessary for that.

69 gr Sierra HPBT out of a 1/9 twist over something like 25-26 of Varget is the sweet spot for me, be it an AR platform or 223 bolt action.
 
I shoot out to 400 these days. It isn't just about shooting a longer bullet. The more bullets your barrel can stabilize, the more options you have to play with. Especially when you don't reload, as many bullet weight choices are made for you. I haven't found an 68-69gr bullet yet that any of my ARs likes as well as a 52gr and 75gr. If I had a 1:9 barrel that didn't stabilize 75gr bullets, the choice to shoot 52gr bullets would be made for me. That is true for both Hornady and Nosler OTM bullets.
 
I haven't tryed any bullets heavier then 55grs yet but my PSA 1/7" shoots the federal varmint tipped 50gr sub MOA and minute if clay pigeon out to 300 yard if I do my part with the milspec trigger.
 
My 1:9 will handle everything up to 75 gr. just fine. But that's a 26" barrel on a varmint rifle. It may be different with a AR barrel. Even at 75 gr. as my limit there are bullets I can't shoot though. Heavier bullets are said to stay on course farther and maintain their energy level farther also. I don't know about that. I just know I can't shoot anything over 75 gr. without accuracy problems. I've never heard of anyone complaining about accuracy problems using low weight bullets in a 1:7 barrel. So there doesn't seem to be a good reason not to go ahead and get a 1:7 IMO.

I've seen this topic debated for years. At one time I read comments from people that a 1:7 would spin a light bullet too fast. I haven't seen anyone actually complain about that problem though. Looking around I still see people making that claim though. Here's an example of a quote I found on another forum:

The bullet can blow up. It can only spin so fast before the centrifugal force is so high, it will fly apart.
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Other people said:

I had a similar experience with Winchester 55 gr. .223 FMJ's (Vietnam era M193 Ball) in an 1:8 match barrel. My friend who was spotting for me said that about 10-12% of these bullets would blow up leaving a gray puff of smoke at a range of 40-50 yds. and no hits on the target. After talking with the Winchester tech rep, he told me that the twist was too fast at that MV to keep the jacket together. Hence the blow ups.
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I didn't say this stuff but it's out there. I've fired 40 gr. bullets from my 1:9 and never saw such a thing. I'd be shocked to think that a 1:8 would make bullets "blow up" like the claim says. And they talk about even heavier bullets than 40 gr. doing it. The second quote above mentions 55 gr. bullets from a 1:8 blowing up. It sounds pretty hokey to me and I won't believe it until I see it. I suppose it's possible I had some accuacy issues with the light weight rounds I've fired but "blowing up"??? I don't think so. I'm not even sure about the lighter bullets causing accuracy problems. I just know my rifle doesn't like them for whatever reason.
 
Cee Zee said:
I've never heard of anyone complaining about accuracy problems using low weight bullets in a 1:7 barrel. So there doesn't seem to be a good reason not to go ahead and get a 1:7 IMO.
Click to expand...

Maybe you didn't "hear" me. But either you didn't read my post or you don't take me seriously. OK, I wasn't complaining, but if someone is a studious shot they will notice a difference.....with MY 1:7 DD M4V3 (modified) on sand bags and very careful control, I can see my shots at 50-100-200 yards go from coin size groups with 62-69gr to baseball size groups with 55gr. I guess in some kind of real shooting scenario that doesn't matter much, but it certainly drives me to 62gr bullets.
 
Are you comparing comparable ammo? Expecting cheap 55 grain blaster ammo to keep up with premium heavier offerings isn't exactly fair.
 
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