hi there i need some help. i am building a ar15 varmint,table gun. i am now ready to order my barrel, when ordering one must choose a 1:8 twist or 1:9 twist, whats the difference? seems to me that little of a difference will not make much difference on paper. gun will be a 600-1000 yard gun. what should i choose?
1:8 or 1:9
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HOLY DIVER
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if i was shooting 600-1000yards i would look at a 1:7 twist......in fact i think i would look into a dpms 308 ar style rifle for that kinda range
Taurus 617 CCW
Member
I put a Noveske 1:7 14.5" barrel on my AR and never looked back. It has been the best purchase I have ever made for an AR.
Fatelvis
Member
I prefer minimum 1:8 twist.
Uncle Mike
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1:8" if you must but a 1:7" would be better if your going to shoot the long, heavy bullets out there at 1K.
W.E.G.
Member
What the heck does "punch" mean?
Are you talking about kinetic energy?
Rest assured, no matter what bullet you shoot out of a .223 at 1000 yards, the only "punch" it has at 1000 yards is enough energy to make it through the target-backer.
Are you talking about kinetic energy?
Rest assured, no matter what bullet you shoot out of a .223 at 1000 yards, the only "punch" it has at 1000 yards is enough energy to make it through the target-backer.
Jim Watson
Member
80 gr SMK is going to arrive at 1000 yds with 225 ft lbs.
About like a light bullet .38 Special.
Rifling twist has no effect on "punch" just stability.
About like a light bullet .38 Special.
Rifling twist has no effect on "punch" just stability.
mljdeckard
Member
And remember, the original rifling was 1/12. The army was using 55 gr bullets that were much more rounded, more like a football. They were intentionally making them yaw, it was very common to get sideways imprints of the bullets going through the paper at longer ranges. When they switched to the A2, they also switched to a 62 gr bullet, which is longer and the edge that touches the rifling (the ogive) is flat. The reason for 1/7 rifling is that tracers need a bit more stabilization than regular rounds. (I have fired tracers in machine guns, but never in an M-16.)
In my experience, 1/9 handles everything very well, including 55 gr bullets. Particularly Barnes all-copper bullets, because they are a bit longer and flatter than lead bullets. The twist rate has just as much to do with the SHAPE of the bullet as it does the WEIGHT.
In my experience, 1/9 handles everything very well, including 55 gr bullets. Particularly Barnes all-copper bullets, because they are a bit longer and flatter than lead bullets. The twist rate has just as much to do with the SHAPE of the bullet as it does the WEIGHT.
Maverick223
Member
It will generally make a smaller hole in the paper, because it didn't keyhole the heavy bullet that you tried to use in the 1:8" twist.
To the O.P.: I would suggest going with a different chambering if you really want to reach out to 1k, the 6.5Grendel is probably the best candidate in a AR-15 platform and the .260 is even better in a AR-10 (but will be heavier by a good margin). If you are determined to go with .223, it will get the job done, but I would want a 1:6.5" or at least a 1:7" twist to handle the heavier (read: longer) bullets with a high BC.
sarduy
Member
1:7 so you can use the 55gr for closer range and the heavier bullets for long range
Shadow Man
Member
Like Maverick said, for reliable 1K hits, the 6.5 Grendal would be a better performing cartridge, yet, I will answer your question: out of the choices, 1:8 would be better, but may I suggest looking around for a 1:7 twist, or one even lower? Also, be careful of the length of bullets you start loading to get that high BC, eventually the rounds will no longer fit in the magazine. Now, if you had a bolt gun, it would be a totally different story...
hoppes-no9
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mljdeckard,
Perhaps I am misreading your post, but it seems you are saying that in a given barrel, longer bullets stabilize better than shorter bullets of equal weight?
If that is indeed what you're saying, that's wrong. Shorter bullets will stabilize better (unless you get into the area of "overstabilization"). Stated another way, longer bullets need faster twist to stabilize.
twist calculator
If I misunderstood your post, my apologies.
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Maverick223
Member
I calculated it to be 288ft/lb of energy with a 90gr projectile moving at 2500fps (which should be about right for "best case"), whether that is good enough for anything beyond paper is up to you. Personally, it is a little low for my taste.
mljdeckard
Member
I'm sorry if I was unclear, I was saying that 1/9 is a great compromise that will handle everything from 55 gr to 62 gr. I honestly haven't tried anything heavier than that.
Maverick223
Member
Huh? In the above quote I was referring to the fact that a heavy bullet would keyhole rather than punch a clean hole. FWIW, I'd rather not get shot with anything, including a BB gun, doesn't mean I consider that to have adequate power either, though 288fpe would be fine for most varmints (assuming P-dogs, G-hogs, et cetera).wishin said:
I shoot 77gr black hills factory loads in my 9 twist all the time, and it doesn't keyhole. In fact it shoots extremely well, and difference in group size between the 77gr, 62 gr, and 69gr is almost certainly inconsistency on my part, not my rifle.
T.A.Sharps
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I was in the same worry as the OP, being more accuracy oriented with my purchase.
Basically the twist rate is directly related to the bullet you want to, or can shoot.
I ended up going with a 1/9" twist barrel for half the reason I wanted a heavier/stiffer barrel for my 16" carbine, and the other half is that 95% of all 223/556 ammo available in my area is 55gr.
I would really prefer to shoot 60-80 grain bullets, but I don't reload yet, and that ammo is more expensive and has less commercial options locally.
I would rather of had a black coated 18" bull barrel with a 1/8 twist, and all the ammo to shoot, but it didn't seem realistic, if I start reloading I can always get a new Krieger barrel and free float tube for it.
Basically the twist rate is directly related to the bullet you want to, or can shoot.
I ended up going with a 1/9" twist barrel for half the reason I wanted a heavier/stiffer barrel for my 16" carbine, and the other half is that 95% of all 223/556 ammo available in my area is 55gr.
I would really prefer to shoot 60-80 grain bullets, but I don't reload yet, and that ammo is more expensive and has less commercial options locally.
I would rather of had a black coated 18" bull barrel with a 1/8 twist, and all the ammo to shoot, but it didn't seem realistic, if I start reloading I can always get a new Krieger barrel and free float tube for it.
keyhole means the bullet hits the target sideways, or really any way besides point first. This can happen if the bullet is not spun fast enough to stabilize it. The longer/heavier bullets need to be spun faster to stabilize. For your needs an 8 twist would work, but if you handload and are thinking you might go to 80 or above, it wouoldn't hurt to get a 7 twist. The only disadvantage is you could have issues if you shoot really light bullets(like 40 gr) with really thin jackets. I've heard you can basically spin the bullet apart, although I've not ever witnessed this happening.
T.A.Sharps, I've been using 68 gr. Ultramax ammo in my mini-14 and have been very pleased with it; reasonably priced too.
http://www.ultramaxammunition.com/rifle.php
http://www.ultramaxammunition.com/rifle.php
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