AR barrel twist and other info needed

AR barrel twist and other info needed

This is a discussion on AR barrel twist and other info needed within the General Firearm Discussion forums, part of the Related Topics category; Looking for some AR15 5.56 knowledge here folks. Posted in this section because if I purchase one itíll be for plinking and target shooting and ...

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    Senior Member Array AndyC's Avatar
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    AR barrel twist and other info needed

    Looking for some AR15 5.56 knowledge here folks. Posted in this section because if I purchase one itíll be for plinking and target shooting and what not instead of home defense. One thing Iím curious about is barrel twist. Iím seeing 1:7 and 1:9 a lot as I look around at them in stores. Which is better or does it matter a lot in the grand scheme of things? Different twists require different ammo grains? Any other helpful information when just looking at them? This will be my very first one so not looking to build right now, just looking at budget friendly models right off the shelf that I can just make a range toy out of it. Not looking to make like a mile long shot with it, use it for home defense, or hunt with it just plink cans and what not. Prolly this first one will see a maximum of 500 rounds a year 100% being at the range so just looking to get my feet wet with a budget friendly model and see how I feel about the platform and how much I enjoy shooting it before spending higher dollar money.

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    The rate of twist is based on bullet length. Some say bullet weight, but heavier bullets are longer, and it's the length that causes stabilization issues. In general, longer bullets require a faster rate of twist. Your typical 55-grain .223 will do fine with 1-12 twist but 60- some to 70-some grain bullets will not. The fastest twists like 1-7 can be too fast for the lighter bullets. Either 1-8 or 1-9 is a good "all-purpose" rate of twist for general shooting purposes.

    My AR is 1-8 and 55-grain reloads shoot fine.
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    My Colt LE6920 has a 1:7 twist rate. My Armalite Target rifle with a bull barrel has a 1:8 twist rate. My Stag Arms and Windham Weaponry ARs have 1:9 twist rates. They all seem to shoot 55 to 75 grain ammo well.
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    Senior Member Array AndyC's Avatar
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    So for my intended purposes 1:9 would be ideal, however if I saw one and loved it and it was a good price I wouldnít regret or have problems with 1:7 or 1:8?
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    In very practical terms, unless you're looking for match-grade accuracy, the difference won't be noticeable.

    Rifling twist rate is typically optimized based on the length of the bullet. Longer bullets require a faster spin rate to stabilize than shorter bullets. Given a specific caliber (or bore diameter), a longer bullet will be heavier than a short one, so that translates into advice commonly provided about twist rates based on bullet weight.

    For the AR-15/M-16, the original bullet was 55 grains and I believe the rifling twist rate was 1:12 (1 complete revolution in 12 inches of barrel). When the 62-grain became available, it was observed that the bullets yawed in flight which was a detriment to accuracy. Current military carbines models use a 1:7 rifling twist rate.

    There is a practical limit to twist rate, but that's less of a consideration for small bores in the .22" range. If the bullet spins too fast, it can disintegrate in flight due to centrifugal forces exceeding the structural capability of the jacket or the core, which will limit downrange effectiveness. More of a problem for the larger bore sizes since centrifugal force increases with the square of the diameter, thus for a given rotational speed a .30 cal bullet will have nearly double the centrifugal force acting on it that the .22 cal bullet does.

    Here's a useful summary: https://blog.cheaperthandirt.com/ar-...ist-explained/
    Last edited by gasmitty; November 24th, 2018 at 07:00 PM.
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    Quote Originally Posted by gasmitty View Post
    In very practical terms, unless you're looking for match-grade accuracy, the difference won't be noticeable.

    Rifling twist rate is typically optimized based on the length of the bullet. Longer bullets require a faster spin rate to stabilize then shorter bullets. Given a specific caliber (or bore diameter), a longer bullet will be heavier than a short one, so that translates into advice commonly provided about twist rates based on bullet weight.

    For the AR-15/M-16, the original bullet was 55 grains and I believe the rifling twist rate was 1:12 (1 complete revolution in 12 inches of barrel). When the 62-grain became available, it was observed that the bullets yawed in flight which was a detriment to accuracy. Current military carbines models use a 1:7 rifling twist rate.

    There is a practical limit to twist rate, but that's less of a consideration for small bores in the .22" range. If the bullet spins too fast, it can disintegrate in flight due to centrifugal forces exceeding the structural capability of the jacket or the core, which will limit downrange effectiveness. More of a problem for the larger bore sizes since centrifugal force increases with the square of the diameter, thus for a given rotational speed a .30 cal bullet will have nearly double the centrifugal force acting on it that the .22 cal bullet does.

    Here's a useful summary: https://blog.cheaperthandirt.com/ar-...ist-explained/
    Excellent article thank you!

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    Quote Originally Posted by AndyC View Post
    So for my intended purposes 1:9 would be ideal, however if I saw one and loved it and it was a good price I wouldnít regret or have problems with 1:7 or 1:8?
    Correct!
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    If you're not shooting in competition, any of the three is fine. What you obviously don't want is an older model with the 1:12 barrel, but you're not likely to find one in a store.

    You can shoot 77 grain defensive loads in a 1:9 and you can shoot varmit loads in a 1:7, but as @gasmitty says, you might possibly experience a bullet break up (in-flight) with older ammunition. Many of the newer varmit loads from major manufacturers will shoot just fine in a 1:7.

    Most carbines sold today will have 1:7 or 1:8 twists. Older model carbines might have a 1:9. Carbines (16 inches of barrel length or less) will need heavier bullets for defense, however 55 and 62 grain loads will shoot just fine and serve both purposes.

    The only tricky thing is to make sure the chamber (barrel) is marked "5.56 NATO" or "223 Wylde" instead of "223 Remington". You can shoot any ammunition designed for the gun in the first two, and only .223 Remington loadings in the one so marked. The cheapest ammo for fun shooting will be 5.56 NATO.
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    Well I went to my local gun store and he had 3 in stock that were more in my budget friendly price range. Between the 3 one didnít have any sights at all on it it was an Anderson (not sure on actual model) with 1:8 twist, one only had a front idk I call it a standard A sight with no rear sight at all it was a palametto state armory (again not sure of the actual model) with a 1:7 twist, the third one had front and rear sights on it and was a del-ton DT sport mod 2 with 1:9 twist. I ended up bringing the del-ton home, it was actually the cheapest between the 3 in my range and also with both sights already on it it was ready to just come home and shoot out of the box. I know palametto was probably better, but it was $105 plus I would have needed some sort of rear sight to put on it, so that plus the extra $105 I just passed on it. I think the del-ton will meet my minimal needs of just to have a rifle just to go out and plink with every now and then and handle 500-1000 rounds per year. I also know that I could have had more options and cheaper prices possibly online but I like shopping at my little local places and Iím willing to pay a little more and or miss out on a few more options to do so.

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    For a first AR, just buy a Smith and Wesson M&P. Everything you need, nothing you donít. Throw a rear sight on it and call it a day. Great for plinking, home defense, hunting, or anything else you need a general purpose rifle for. It will shoot any ammo you want from the light varmint stuff to the heavy hunting and long range loads. Itís reliable, durable, and well made.

    Best of all? Doesnít break the bank either.
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    Here you go 16-18 inch barrel 5.56 or .223. Unless you are punching paper for a score at longer ranges it won't madder much and if it did you would be buying a match grade barrel The 1 -7 is made to make the bullet do damage the 1 -9 not so much. The 1 in 8 someones idea of splitting the difference. Most Ar's sold in the last dozen years are 1 in 7. The better a bullet is stabilized the more accurate it tends to be the less stabilized the more damage it does when it hit. As with all things there is a But or two. Bullets that are stabilized to fast can tend to come apart . Not stabilized enough miss the broad side of the barn. Most shoot .223 55gr or 5.56 55 or 62 gr when that is the case it don't really madder much.
    This is just of education it will likely have very little effect on your shooting. look at the graph kind of ignore the stuff at the bottom
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    sgb
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    Quote Originally Posted by AndyC View Post
    Well I went to my local gun store and he had 3 in stock that were more in my budget friendly price range. Between the 3 one didnít have any sights at all on it it was an Anderson (not sure on actual model) with 1:8 twist, one only had a front idk I call it a standard A sight with no rear sight at all it was a palametto state armory (again not sure of the actual model) with a 1:7 twist, the third one had front and rear sights on it and was a del-ton DT sport mod 2 with 1:9 twist. I ended up bringing the del-ton home, it was actually the cheapest between the 3 in my range and also with both sights already on it it was ready to just come home and shoot out of the box. I know palametto was probably better, but it was $105 plus I would have needed some sort of rear sight to put on it, so that plus the extra $105 I just passed on it. I think the del-ton will meet my minimal needs of just to have a rifle just to go out and plink with every now and then and handle 500-1000 rounds per year. I also know that I could have had more options and cheaper prices possibly online but I like shopping at my little local places and Iím willing to pay a little more and or miss out on a few more options to do so.
    If your AR has a Chrome Moly bore (which lowest priced AR's usually do) be sure to keep the chamber CLEAN ........... The military guns have a hard chromed chamber nd bore for a reason, many of the better quality AR's come with a Nitrited bbl which accomplishes the same thing as hard chrome, less corrosion and wear.
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    Senior Member Array AndyC's Avatar
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    Quote Originally Posted by sgb View Post
    If your AR has a Chrome Moly bore (which lowest priced AR's usually do) be sure to keep the chamber CLEAN ........... The military guns have a hard chromed chamber nd bore for a reason, many of the better quality AR's come with a Nitrited bbl which accomplishes the same thing as hard chrome, less corrosion and wear.
    Here are the specs on it from manufacturer:

    Barrel:

    4140 Melonite Steel
    16" Length, 1x9 Twist
    Carbine Gas System
    Threaded Muzzle, A2 Flash Hider
    Manganese Phosphated
    Melonite under Standard A2 Front Sight Base
    Lightweight Profile


    Chamber:

    5.56 x 45mm


    Bolt & Carrier:

    Phosphated 8620 Steel Carrier Assembly
    Carpenter 158 Bolt
    Heat Treated and Plated
    Mil-Spec
    Chrome Lined Carrier Interior
    Carrier Key - Chrome Lined, attached with Grade 8 Screws
    Properly Staked & Sealed Gas Key

    Handguards:

    Carbine Length
    Aluminum Delta Ring
    Single Heat Shield

    Upper Receiver:

    Forged 7075 T6 Aluminum
    A3 Flat Top w/ White T-Marks
    Hard Coat Anodized
    Boreís Surface is coated with dry film lube, over anodized surface
    Mil-Spec
    Ejection Port Cover and Round Forward Assist
    Right Hand Ejection


    Lower Receiver:

    Forged 7075 T6 Aluminum
    Hard Coat Anodized
    Mil-Spec
    Enhanced Triggerguard
    Mag Catch Button
    Semi-Auto
    A2 Grip


    Buttstock:

    M4 6-Position Buttstock
    Commercial Buffer Tube
    Carbine Buffer

    Included:

    1 x 30rd Magazine
    Chamber Flag
    Gun Lock
    Mako Rear Sight

    Weight:

    5.8 lbs. Empty

    Length:

    36.375" Fully Extended
    32.625 Collapsed

  15. #14
    sgb
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    Quote Originally Posted by AndyC View Post
    Here are the specs on it from manufacturer:

    Barrel:

    4140 Melonite Steel
    16" Length, 1x9 Twist
    Carbine Gas System
    Threaded Muzzle, A2 Flash Hider
    Manganese Phosphated
    Melonite under Standard A2 Front Sight Base
    Lightweight Profile

    ..... 1st it says it's Melonite then it says it's Manganese Phosphated with Melonite under the front sight base ......... I always shy away fro less than clear descriptions, my guess s it's a cheep chrome molly barrel.
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    VIP Member Array Eagleks's Avatar
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    For your use, just get one you like and can afford... that's a 1/2 way decent AR. Differences you would notice on twists is at longer distances and the grain you would shoot..... and most would never likely notice the difference, especially at 100-200 yards. Some in my opinion PSA, BCM, Spikes, Ruger.... Rock River a bit more expensive but good and many like their match trigger ... and you can keep going as high as you want. Plan on accessories and the costs..... bag, ammo, magazines, sights you want on an M4 version, etc. Also whether you want the typical length or mid-length. For me, middle length is the only one I will get ... hold both and see what you think I wouldn't recommend DPMS , etc to anyone, myself.
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