View Full Version : Barrel Twist Question
04-30-2011, 8:27 PM
What the heck does it mean b 1x7 and 1x9? Which is better?
04-30-2011, 8:31 PM
how fast the bullet will spin...1x9 is an all around twist generally up to 62 grains..it will shoot heavier rounds but for 62gr and heavier a 1x7 is preferred ( 1x7 is a faster spin )
04-30-2011, 8:36 PM
Does a faster spin make it more accurate? Also, what generally preferred, a 20" barrel or a 16" barrel?
04-30-2011, 8:39 PM
Not sure..but I see Colt and others doing 1x9 on a 20 in barrel but then I see some using a 1x8 twist...I'm a carbine shooter and not into long range with a .223/5.56 round
I;m sure others will chime in and add more info.
04-30-2011, 8:44 PM
The faster (1:7) twist rate will help stabilize a heavier grained projectile
If you're shooting 55gr ammo, a 1:9 twist is fine. But a 75gr projectile through a 1:9 twist from a 16-inch barrel will have problem slicing through the air and affect accuracy
1x7 means that the bullet will make 1 complete revolution in 7 inches of travel down the barrel.
1x9 means that the bullet will make 1 complete revolution in 9 inches of travel down the barrel.
The longer the bullet is (which usually means that the bullet is heavier) the faster it must spin to stabilize in flight.
In an AR chambered in 5.56 Nato the fast twist barrels (1x7, etc) are used with heavier bullets 73 grain and higher for better long range performance. The 1x9 twist barrels are used with medium weight bullets 55-68 grain and the slow twist barrels of 1x12 or so are generally used with 50-55 grain bullets.
Barrel length is usually decided by what use you have for it. 20" barrels for more velocity, longer range shooting and 16" barrels for a more compact, close quarter use.
04-30-2011, 9:34 PM
I've been shopping for an upper. My desired chamber is a .223 Wylde. I've seen at the local gunshop near my office where all their Wylde's are a 1:8 twist. Is that kind of the best of both worlds kind of thing? Not overspinning lighter rounds...but giving enough spin in the case for heavier (longer range)?
Sorry...noob here as well.
04-30-2011, 9:41 PM
I think the belief that a 1 in 7 twist rate barrel can't shoot lighter rounds effectively.
What i've found for my ar ( which has a BCM 1 in 7 twist 16 " barrel ) is that is shoots the regular ole xm193 ball from federal. A no frills 55 gr jacketed 5.56 round. It shot that better then a much heavier and more expensive hornady 72 gr supervarmint round. Mind you i wasn't taking it out past 200 yards apart from some steels at 300 and 400. But at least within 200 yards the lighter round ....for my gun ...... was just as precise if not more so
04-30-2011, 9:45 PM
Agreed. I have shot plenty 45gn urban tap through my bcm 1 in 7, and it works just fine.
04-30-2011, 9:47 PM
I've seen at the local gunshop near my office where all their Wylde's are a 1:8 twist. Is that kind of the best of both worlds kind of thing? Not overspinning lighter rounds...but giving enough spin in the case for heavier (longer range)?
Yep. That's plenty of twist rate.
05-01-2011, 9:05 PM
what ammo weight for say a 1:7 twist but 14.5" never looking to reach out past say 200 yards more so 50-100 on average. thanks
sorry if off topic not meaning to threadjack.
05-01-2011, 9:11 PM
55-77gr. If you want to find the best accuracy you can get out of it, you should expereiment with many different loads.
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