The Down Range Forum
Member Section => Tactical Rifle & Carbine => Topic started by: garand4life on October 21, 2009, 06:40:01 PM
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I have an AR15 with a barrel twist of 1/9. I also have quite a stock pile of 75grain Hornady TAPFPD .223. Will the 1/9 twist stabalize this heavier round sufficiently to maintain a 50-100 yd effective range or will this thing fly off the handle?
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From 6mmBR.com
Twist Rates
223 Rem Remington barrel Twist rateThe .223 Rem shoots a wide range of bullets very effectively, from 35gr flat-based varmint bullets, to ultra-long 90gr VLDs. However, you'll need the right twist rate for your choice of bullet. For max velocity and accuracy with the lightest bullets, a 1:14" twist may be ideal. More versatile is a 1:12" twist that will allow you to shoot the popular 60-64 grain match bullets. (However, a 1:9" twist is needed for the steel-core 62gr bullet used in the M855 military loads, because that bullet is as long as most 70-grainers.) For normal lead-core jacketed bullets, a 1:9" twist will let you shoot up to 73gr bullets. Since most .223 Rem shooters prefer bullets in the 50-73gr range, a good "do-it-all" solution is a 9-twist, unless you're a Highpower competitor.
For long-range match purposes, long, high-BC bullets are favored for their ability to buck the wind. You'll want at least a 1:8" twist to shoot the 77gr and 80gr MatchKings and 80gr Bergers. To shoot the new 90gr pills, a 1:6.5" is recommended, though a true 1:7" will work in most conditions.
Overall, what twist rate is best? For varminting we like a 12-twist. The slower twist will give you a bit more velocity, and minimize the risk of jacket failure at high rpms. For general use, an 8-twist barrel will let you shoot the excellent 77gr and 80gr Sierra MatchKings and nearly all varieties of non-tracer milsurp ammo. We'd only select a 1:7" or faster twist barrel if we had a need to shoot the 90gr VLDs.
Barrel Twist Rate 1:14" 1:12" 1:9" 1:8" 1:7" or 1:6.5"
Max Bullet Weight 55gr FB 65gr FB 73gr BT 80gr BT 90gr BT VLD
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So..... that's a maybe?
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The 75 Grain Wolf .223 load was found to be quite accurate in a 1 in 9" twist barreled AR-15. Bill T.
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Sounds like what you have (1:9) is "good enough" for what you want, but to get the most out of your rifle you would be better off with a 1:8.
Judging by the ranges you mentioned (50 - 100 yards ) you are not planning on shooting Bulls eye competitions with it, 1:9 should be fine.
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From 6mmBR.com
Twist Rates
We'd only select a 1:7" or faster twist barrel if we had a need to shoot the 90gr VLDs.
Barrel Twist Rate 1:14" 1:12" 1:9" 1:8" 1:7" or 1:6.5"
Max Bullet Weight 55gr FB 65gr FB 73gr BT 80gr BT 90gr BT VLD
What is the twist rate of the M16?
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Garand4life,
My understanding from talking to a friend that does 100-600 yards with .223 is that 1 in 9 will stabilize anything for under 200 yards just fine. He, and many of his fellow shooters, are using between 1 in 7 and 1 in 8, he is using 1 in 7.75, for 75 to 90 grain.
He instructed me that at a hundred yards you can get by with a lot if you are not trying for one hole groups. Fox and Coyote have a large enough kill zone to be very forgiving. When you go for more precision it is a total load and gun package. Work up loads considering bullet weight, bullet speed and head space (oal).
Bottom line, for 75 grain in a standard 1 in 9, I'd load and shoot 'em. If you keep the speed down in a standard range they should do just fine.
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I loaded 75 gr BTHP to shoot out of my 24" AR (1:9 twist). They were insanely accurate. I just loaded up some different rounds in 1/2gr increments and stuck with the tightest group. I could easily keep a 30rd mag in nickle sized group at 100yds.
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What is the twist rate of the M16?
1:7. They need an extra fast twist to stabilize tracers because the bullets are so long. 1:9 is good for everthing except tracers.
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At moderate ranges, a 1 in 9 is great. Zombies will never know the difference.
With a bipod, my Sig556, 1in 9, 16" Barrel, can keep a softball size group at 100 yds. Through 62gr rounds.
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I was googling Hornady TAP and found this video test of the 75 grain TAPFPD .223 through a 1/9" 24" Bushmaster Varmit rifle. Showing that the round can be quite accurate in a 1/9 twist barrel. Nice round!
http://www.youtube.com/watch?v=g95JPyZpfDQ
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I was googling Hornady TAP and found this video test of the 75 grain TAPFPD .223 through a 1/9" 24" Bushmaster Varmit rifle. Showing that the round can be quite accurate in a 1/9 twist barrel. Nice round!
http://www.youtube.com/watch?v=g95JPyZpfDQ
It would have been nice for him to group on paper instead of steel. The groups still were not that impressive.
Work up your own loads, you can probably do better.