Is 1:7 too fast?

Discussion in 'AR-15 Discussion' started by ScottA, Dec 25, 2011.

  1. ScottA

    ScottA FAA licensed bugsmasher Lifetime Supporter

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    I'm looking to do a semi-build on an AR. The Palmetto State Armory complete uppers seem to be getting a lot of good reports and are very reasonably priced. But it seems everything they are making is in a 1:7 twist. This seems pretty aggressive for a general purpose carbine.

    Would you be concerned about 55 grain bullets with a 1:7 twist? Or should I really be looking for a 1:8 or 1:9?

    My intent is a rifle that will be used for plinking, HD, and coyotes. I'll probably look at a different upper for varmints down the road.
     
  2. EW1066

    EW1066 Member Supporter

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    The only rounds that seem to have a problem with 1:7 is "varmint" rounds. I have seen video of those disintegrating about 20 yards [ame=http://www.youtube.com/watch?v=GTJaNHjEa_k]Light bullets in a fast twist rate, through an AR15 - YouTube[/ame] after leaving the barrel. As far as 55gr fmj is concerned. I shoot those out of my Daniel Defense barrel without issue. Have not had an opportunity to shoot HP yet. I guess they could self destruct since they don't have the same structural integrity as fmj bullets.

    Merry Christmas

    EDUB
     

  3. Quentin

    Quentin New Member

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    I wouldn't be worried about 55gr with a 1:7 twist but wouldn't go much lighter. Since you're thinking about a true varmint upper later, 1:7 would be ideal right now as it gives you a lot of flexibility including performance with heavier bullets.
     
  4. Snakedriver

    Snakedriver New Member

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    I've been shooting AR's longer than most here have been alive and I'll never be convinced that spinning the crap out of a light bullet will make it accurate. For that reason I went with a 1:9 twist in a new RRA recently and it is superbly accurate with 55 gr. bullets.

    I go back to when I qualified expert with a M16A1 in Army Basic Training. The A1 I used was a 1:12 twist if I recall and there was only one choice of bullet and it was a 55 gr. bullet. The old M16 was deadly accurate out to 300 meters without any adjustment to the iron sights needed, even with the slower twist rate.

    I probably have at least 10,000 rounds of 55 to 62 grain 5.56/.223 ammo stored up and I am positive that I'll never ever be shooting heavy bullets through my AR. I also plan on doing all my shooting at ranges of 200 yards or less.

    I know it's probably available somewhere, but I've never seen any heavy weight 5.56 /.223 ammo over 62 grains for sale anywhere. I also reload this caliber, so I could obtain the heavy bullets if I wanted, but why bother. I am also fairly sure I'll never need to fire tracers or make shots in excess of 500 yards with my AR and that's the reason the .mill went with the fast 1:7 twist.

    Everyone makes a big fuss about having the fast twist barrel in their AR, but it's just not necessary in my opinion for what I want to do with mine. As usual, if that's what you want, well good for you be my guest, freedom of choice is what makes this Country great.
     
    Last edited: Dec 25, 2011
  5. mjkeat

    mjkeat New Member

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    I would stick with 1:7 as I shoot 55 and up.
     
  6. Sniper03

    Sniper03 Supporting Member Supporter

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    Scott,

    A little fast! You will not achieve peak accuracy from that combination although they will shoot fairly ok as far as just shooting. Depends on what you want out of the rifle as far as precise accuracy. I prefer the 1:9 in The tactical style AR-15. And as was stated earlier if you ever go to some of the lighter softer varmint bullets the 1:7 can spin them apart. If you were planning on shooting rounds in the mid to high 60s or heavier the 1:7 would be fine.

    03
     
  7. AgentTikki

    AgentTikki New Member

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    I have put a lot of rounds, 55 grain rounds in the thousands, pmc .223, m193, xm193, and mfs russian steel case stuff. Never had a promblem with 55grainers. You'll be fine. You're not trying to get 1/2 moa groups are you? For general plinking shooting, and gunfights you're good with 55 gr fmj.
     
  8. locutus

    locutus Well-Known Member Supporter

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    I use 55 and 62 grain bullets. My preference is 1-9.
     
  9. Axxe55

    Axxe55 The Apocalypse Is Coming.....

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    i'm curious as my 16" barreled AR has a 1-9 twist, i shoot mainly 55gr. fmj ammo, would i be better off with the 1-7 twist given my ammo choice?
     
  10. AgentTikki

    AgentTikki New Member

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    No. 1x9 is perfect for your shooting needs.
     
  11. Axxe55

    Axxe55 The Apocalypse Is Coming.....

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    thanks tikka, i thought so, but was unsure after all the different twists were mentioned. so if i wanted to shoot heavier bullets then use the 1-7 twist barrel?
     
  12. Sniper03

    Sniper03 Supporting Member Supporter

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    55,

    The 1:9 will handle up to 69 grain bullets very well. What you need to also consider the 55 gr. bullets which the 1:9 will shoot very well also are less expensive normally than the other weights and are in more supply regarding availability! Still I think the 1:9 is the way to fly all around vs. the 1:7! Not that the 1:7 is a bad twist rate.

    03
     
  13. Axxe55

    Axxe55 The Apocalypse Is Coming.....

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    thanks for the information 03. i pretty much shoot the 55gr weight bullets, but it nice to know that i could go a little heavier if i wanted to or found a really good deal on a heavier bullet.
     
  14. 1stMarine

    1stMarine New Member

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    Anyone other than me remember that when the ar first came out it was a 1:17 twist? (Just marveling about how unstable that'd be) anyway regardless of bullet weights the tighter the twist the more penetrating power and stability the round will have, conversely the less twist will give the round more of a chance to tumble and fragment when it hits flesh doing more damage and cutting down on overpenetration. There is however a considerable drop in longer range stability. Just try ro reason with yourself based on this and then worry about what type of bullet weight you're going to use. Having your heart set on 55gr fmjs seems a bit odd. Id probably go for a 1:11 because I use my ar for home def and varmint hunting under 200m so I'm looking for a rou d that imparts all energy in the body and doesn't exit. However if you're just target shooting, or using it for say 400-500m go with something like a 1:7. Also (I know I'm being completely obvious here) but if you put a heavy say 65gr roung through a faster twist rate you'll literally be stripping out the rifling with each shot killing your barrel making you to go to a less aggressive twist rate. On the other hand a light round going out of a low twist rate barrel won't be as stable as a heavier round out of the same barrel, it also won't damage the barrel, but longer ranges could prove difficult.

    Never Forget.
     
  15. Quentin

    Quentin New Member

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    Don't know about early prototypes but by the time the AR15 went to Vietnam its twist rate was 1:14" and as you said it did have a reputation for tumbling and fragmenting in the enemy.
     
  16. AgentTikki

    AgentTikki New Member

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    +1

    I would like to add that with today's ammo selections, I'm really surprised that more builders/manufactureres aren't going with the 1x8, like the S&W. 1x8 really seems to be where's its at, unless your shooting lw varmint rounds or super long or tracer ammo.
     
  17. Snakedriver

    Snakedriver New Member

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    Man Quentin you really had me stumped there for a minute and I had to go do some research. Only the very earliest M16's (Models 601 & 602) in the early 1960's, that were bought mostly by the Air Force, had the 1/14 twist barrels. I never knew this, but I'm never too old to learn something.

    When the M16A1 upgrade arrived with things like the bolt forward assist, the twist rate had been increased to 1/12 and stayed that way until the M16A2 was adopted with the current 1/7 twist.
     
    Last edited: Dec 27, 2011
  18. Quentin

    Quentin New Member

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    Same here, Snake, there's a lot that happened early on in AR/M16 development and we all learn something new here and there.
     
  19. pfatz

    pfatz New Member

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    AR 15 Twist & Ammo

    I am a Gunsmith. Now retired. I own a Wilson AR made some time ago. Wilson guarantees 1/2 MOA(?) with Factory 69Grain Ammo I believe. My version is 1:9 if I remember correctly.

    I believe the Spec Op types may be shooting 69G or I've read 77Grain. That is just what I've read and I don't remember any discusion of twist. I've recently read that some special HP ammo has been Ordered & Authorized for use by Spec Ops. Possibly to become universal to the Army in the future.

    I believe the Globe & Anchor boys have an entirely different take on ammo.

    Since I am Ex Army, I follow them mostly.
     
  20. mjkeat

    mjkeat New Member

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    The SF guys used match grade stuff when I was in. They gave us a small lot of it as we began to run low. It was heavier than our green tip but I don't remember what grain.

    If NATO would get w/ the times and remove ammo restraints it would sure level the playing field.

    We all used 1:7
     
    Last edited: Dec 27, 2011