Can someone explain to me the positives/negatives or advantages/disadvantages and differences between 1:9 twist barrels and 1:7 twist barrels? It seems like with most brands the 1:7 twist is an upgrade.
I'm no expert, but here's what I know. The 1:7 twist can stabilize heavier bullets more so then the 1:9 twist rate. The 1:9 is the most common of the 2 when it comes to factory builds and for the most part, custom and home builds as well. The 1:7 is a choice for many home and custom builds as well though. 1:7 twist has it advantages over 1:9 which is why it's considered an upgrade from the 1:9.
I'm sure there's more to it then this, but that's what I've picked up on it. Hope it helps even a little.
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Last edited by GlockMeister; 08-05-2008 at 12:48 AM.
The heavier bullets only really come into their own at longer ranges. If you're not going to be shooting at over 300 yards and unless you're getting into competitive shooting, a 1 in 9 will probably be all you'll need. I'm a middle of the road guy so I got a 1 in 8 and shoot 75-80 gn bullets at up to 600m. Would a 1 in 7 be better for me?? I don't know, but on a good day I can put all the rounds in the x-ring at 600m with what I've got.
Hey wun, is then 75gr too much for a 1:9 twist? If so, what about 69gr.?
I'm no expert but I believe that the 62-69 grain bullets are supposed to give the best performance in the 1 in 9 twist. I think that the 75 is too heavy to be properly stabilised in it. I do know that my 20", 1 in 8 gives fairly good performance with the 62gn RG SS109 up to about 3-400 metres and excellent performance with 75 & 80 gns up to 600. Actually it's a tie between the 75 gn Hornady & the 80gn sierra but I've never managed to get hold of enough 77gn Sierra to try yet.
EDIT: For info, in the UK, SS109 surplus ammo is much more common (nato spec) than the 55gn stuff so we tend to prefer the slightly faster twist rate.
Last edited by wunhunglo; 08-05-2008 at 03:27 AM.
Reason: Old fart afterthought.
If you can get it for the same price, get the 1:7. You (theoretically) cannot "overstabilize" a bullet. The 1:7 will shoot the 69gr and heavier bullets, while the 1:9 will only shoot up to the 69gr reliably, and sometimes not even that. I prefer the 1:7 for that reason alone.
There are people that have 1:9 barrels that shoot 75gr bullets, but this varies per rifle. If it's a huge price difference, and you don't plan on shooting the 75gr bullets at all, then don't sweat it. If it's the same price, or even a little more, I would personally say to go for the 1:7.
I know it's not reccommended to shoot a .223/5.56 deer hunting, but if I were going to try to deer hunt with it, I would want to shoot the heaviest bullet I could find. Would any performance be lost shooting the lighter bullets in the 1:7? Thanks for all the input!
I shoot a krieger barreled Bushy with a 1:7 twist, 20 inch free floated. For fun I go shoot sierra 69 grain HPBT. For competion I shoot the 77 grain HPBT sierras. Do the 8 grains make a difference? You bet they do...in my head !!!
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If you can get it for the same price, get the 1:7. You (theoretically) cannot "overstabilize" a bullet. The 1:7 will shoot the 69gr and heavier bullets, while the 1:9 will only shoot up to the 69gr reliably, and sometimes not even that. I prefer the 1:7 for that reason alone.
There are people that have 1:9 barrels that shoot 75gr bullets, but this varies per rifle. If it's a huge price difference, and you don't plan on shooting the 75gr bullets at all, then don't sweat it. If it's the same price, or even a little more, I would personally say to go for the 1:7.
Just my thoughts....
Hey At4rxj, I do want to shoot heavier bullets, albeit probably much less than 300 yards. Also, does barrel length come into play because I really want to stick with a 16" barrell. JT Distributing has a chrome lined 16" barrell with 1:7 twist.
Barrel length does come into play, but to my understanding, with a shorter barrel you want a faster twist like 1:7 or 1:8.
You shouldn't see any adverse effects shooting lighter bullets in a 1:7 barrel. If you get down to extremes you may, but typically you see 50-75gr bullets, and the 1:7 would handle those perfectly.
The barrel you name above sounds perfect. Do you have a link to it?
Barrel length does come into play, but to my understanding, with a shorter barrel you want a faster twist like 1:7 or 1:8.
You shouldn't see any adverse effects shooting lighter bullets in a 1:7 barrel. If you get down to extremes you may, but typically you see 50-75gr bullets, and the 1:7 would handle those perfectly.
The barrel you name above sounds perfect. Do you have a link to it?
J&T 16" DS-4 CAR Kit The last option is Barrel and they have a 1:7 Twist Gov't Profile Chrome lined barrel for a $50 upcharge.
Yeah, I see it. That's a good deal. You're paying the $50 for the chrome lining, though, not the 1:7 twist (they also have a 1:7 non chrome lined with no up-charge)
I'd go with the 1:7. You won't see any difference shooting the lighter bullets... The chrome lined part is up to you. Personal preference in my opinion.
Here's another variable that can come into play as far as which bullet weights a particular gun will shoot well: leade or freebore. As I understand it, this is the amount of space in the front of the chamber (where the bullet is inserted) that is not rifled.
From what I understand, there are differences between a true .223 Winchester chamber and the 5.56x45 NATO chamber. And, the "Match" designation may indicate that there is a slightly longer leade (or freebore) to allow heavier and longer bullets to chamber without contacting the rifling.
In my particular experience, I have a Colt Match HBAR chambered in 5.56x45 NATO, 1:7 twist rate, 20" length. If I stick with 62 grain or heavier bullets, I get great accuracy. But, if I shoot 55 grain bullets, my group sizes increase by several inches.
So in my case, I really don't know if:
1) the faster twist rate cause the lighter bullets to "overstabilize"
2) the "Match" designation means I have a longer leade causing the shorter 55 grain bullets to wobble before engaging the rifling which affects accuracy
3) or some combination of the 2 above
What I do know absolutley, from extensive testing/shooting with all kinds of factory loads, is that with my gun I must stick with 62 grain or heavier bullets. If I shoot 55 grain bullets, I get poor/frustrating groups even at short ranges of 50 yards.
Since the 1:7 doesn't have any problems shooting the lighter bullets, why does anyone even buy the 1:9?
To me this is the post/question of the day. I would love to hear more opinions.
It has been my understanding that too fast spin on a light bullet will cause a wobble jut like too slow a spin for a heavy bullet. I'm not sure if this will really come into play with the bullets and velocities of the .223/5.56 but I have an uncle that built a 7mm STW. He then loaded some bullets with 110gr TNT hollow-points. The end result was extremely poor accuracy - more than you would expect from just expect from a particular rifle "not liking" the bullet. We're talking inches off at 100 yards.
That is an extreme example - again, I'm not sure that 1:7 - 1:9 twist rate is gonna make a big difference for a 16" barrel and a difference in bullet weight of 10-15gr.
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