Gunsmithing  1/7 or 1/8 twist?

NCHillbilly

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  • Jul 7, 2012
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    It's time to build another rifle. It won't be the most practical, but I've got a long range itch to scratch. My plan is to purchase an assembled upper in .223 wylde, with a 20" to 24" inch heavy barrel. I'll be feeding it 69 to 77 gr pills. My question is: which would be the better twist rate for what I'm doing, 1/7 or 1/8? I don't have the tools to build the upper myself, so spec-ing out a bare barrel is out of the question. there are many more options with the 1/8 twist, but if the 1/7 is better, I'll just have to beat the bushes till I find what I'm looking for.
     

    Lunchbox27

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  • Mar 23, 2017
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    A 1:8 twist will handle 69-77 grains without issue. If you are looking for a solid upper, look at White Oak Armament.
     

    padom

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  • Mar 13, 2013
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    Compass Lake Bartlein or Kreiger upper or a White Oak Upper would be my only choices. They both shoot lights out and Ive had many.
     

    Iamero

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  • Feb 14, 2017
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    I agree with Padom. I have a 1:7.7 twist Kreiger on my 20" AR and it is stupid accurate. I don't know if I could go back to a mass produced barrel after owning one. It'll shoot 50gr ammo if I want, but is extremely accurate with IMI 77gr Razorcore (which I believe loads 77 SMKs).
     

    NukeMMC

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    Mar 3, 2009
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    I had a CLE Kreiger 7.7" NM service rifle that shot 69s and 80s very well. Got me into Master Class. Bought one of their space gun uppers, a 24" 1:7.7" twist that was about 100fps faster than the service rifle and scary accurate with 80s at 600. I also had a WOP service rifle that had a 6.5" twist Pac-Nor 3-groove. That rifle shot 69s and 77s well, but the 80gr SMKs and 90gr JLKs were AMAZING.

    I have a Rainier Ultramatch 18" SPR on my MK12 clone that is 1:8" twist. It shoots 77s and 75s very well but the 80s just wont make it in that barrel.
     

    CoA 1

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    Nov 14, 2017
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    Ive had really good results with 77s in 1:7 barrels in the 14.5-18" range. Longer barrels, your probably fine with the 1:8 but if you really want to push the range of that cartridge I would stick with the heavier 77grain pills and a 1:7 barrel.
     

    BCP

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  • Dec 4, 2008
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    7 or 8 twist are both fine

    I prefer 18" rifle gas in an AR15 anything longer and it starts getting to big/heavy

    223 24" isn't enough for a long range 223 unless you mean a ~600 yard plinker. The guys I've seen using a 223 for F class are usually 26-28" and with biggest bullet possible (and lots of varget).
     

    HadesPrecision

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    Not sure if this helps, but my 16" LaRue with 1-8" twist managed a 9" 3 round group at almost 1100 meters with 85gr Barnes MatchBurners. The holes were a little crooked but still not sideways. At 600 meters they were perfectly round clean holes. And this is at a density altitude of -200 feet.

    1-8" twist works just fine ;)
     

    Adah6.5

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    Nov 19, 2017
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    Bergerbullets.com has a twist rate stability calculator that is very useful. Just punch in the info for the bullet you plan to use and if your SG is above 1.5 your good to go. Going with a faster twist then what’s needed can start affecting precision when using average quality bullets. Bryan Litz did testing on this in his book Modern Advancements In Long Range Shooting volume 1. Pretty interesting stuff.
     

    sandwarrior

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    Apr 21, 2007
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    So, here's the problem. It's not so much the barrel as the rifle platform itself. If you want to feed from a magazine, you can only have the overall cartridge length up to 2.26"

    With a 1-7" twist you can stabilize heavier/longer bullets, but you run out of room to feed them through a magazine. But, you can single feed them, if you work up a load with the bullet to or into the lands. With a standard 5.56 throat, that gives you an extra .120" Long enough for 90 SMK's. (the whole premise being to not load a bullet below the ogive in the case.

    For feeding with a magazine, a 1-8" will stabilize the 75 and 77 gr. HP's which will get you to 1k.

    Bottom line is if the latter is all you want to do, no problem get the 1-8" if it's less expensive. The 1-7" twist will give you more lattitude with heavier/longer bullets. And, you can probably find a good one for the same price as a 1-8".

    Also, a long time ago, we were not able to get the concentric standard of manufacturing we see in bullets today. Therefore, we always used to use only as tight a twist as what was required to stabilize bullets. Less of a twist left less of a harmonic imbalance in how the bullet remains stable/accurate in flight. Old time benchresters still live by this and you will see a lot of 1-14" twist .22 cal and 1-13" twist 6mm bench rest barrels. With the higher capability of todays manufacturing in bullets, we can get extremely good accuracy in 1-7" and 1-8" twist using light bench rest bullets.
     

    pmclaine

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  • Nov 6, 2011
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    Can I jump in here to follow this discussion....

    I have a Rem 700 receiver in route that I plan on building a USMC replica M40 in .223 on.

    Im intending 77 grain SMK/Nosler CCs as my only round as that's what I load for my AR.

    My barrel will be a 24 inch Bartlein in Remington Varmint profile.

    I was unsure 1:7 or 1:8 and had read something about 1:7.75 being the ultimate twist for heavies however you determine that fact.

     

    Xander3Zero

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    Aug 10, 2017
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    Can I jump in here to follow this discussion....

    I have a Rem 700 receiver in route that I plan on building a USMC replica M40 in .223 on.

    Im intending 77 grain SMK/Nosler CCs as my only round as that's what I load for my AR.

    My barrel will be a 24 inch Bartlein in Remington Varmint profile.

    I was unsure 1:7 or 1:8 and had read something about 1:7.75 being the ultimate twist for heavies however you determine that fact.

    If you plan to only shoot 77gr then you would be fine with the 1:8 twist, but if you are going with a bartlein, just get their 1:7.7 twist with 5R rifling, they are pretty available.
     

    sandwarrior

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    If you plan to only shoot 77gr then you would be fine with the 1:8 twist, but if you are going with a bartlein, just get their 1:7.7 twist with 5R rifling, they are pretty available.

    Agreed. If you got the tighter twist, if you ever got a notion to, you could shoot the heaviest of the heavies. Meanwhile if you never change from the 77's, it won't hurt you, as I explained above.