ideal rate of twist (MLP firearms and shooting thread)

Discussion in 'The Backstage' started by Frogfur, Jul 4, 2017.

  1. Frogfur

    Frogfur Senior Member

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    *Mod Note*

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    **************************************************************


    I had this discussion with my son around the camp fire last night, so thought I'd put that up here as well.

    In regards to ARs, the ideal twist(for your barrel)for those that shoot 55 grain bullets is 1:9. But if you are sending heavier bullets down range, say 62 grain up to 77 grains a 1:7 or 1:8 twist would be preferable. For you guys who shoot 40 grain and there are some, a 1:12 twist us preferred. Based on a 16" barrel.

    simple as that shooters
    Camp fire fodder..
    20170701_223928.jpg
     
    Last edited by a moderator: Jul 9, 2017
  2. I Break Things

    I Break Things Senior Member

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    I like 1:7 just because it's a touch more versatile. Have had better experience shooting 55-grain through a 1:7 than I have shooting higher grains through a 1:9. I don't have an AR anymore though. I sold it to pay for some of the wedding/honeymoon expenses. Kept my SCAR 16S though!
     
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  3. Meatwad

    Meatwad Senior Member

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    This isn't about purple nurples is it?
     
  4. Malikon

    Malikon ジャンプアップ V.I.P. Member

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    I've clicked this thread twice thinking it said "Twist of Fate"
     
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  5. Frogfur

    Frogfur Senior Member

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    Titty twister..i just disn' t want to openly say it.

    Thank you!
     
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  6. LtDave32

    LtDave32 Sua Sponte Super Mod Premium Member

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    Okay, I'll bite.

    Just had this discussion with Rob on the phone, not three days ago.

    I have an AR, which lower I'd like to add to its purpose by choosing an upper assembly that's different than my current 16" barrel. Sort of build a "platform" from which to run either a longer barrel with a tighter twist in the same caliber for use with heavier, longer bullets, and/or a different caliber altogether that I can pin on, change the mag on, and have another rifle of a different caliber utilizing the same lower as "universal". We were exploring the 6.8 Remington as an alternative. Why a 6.8 Rem? It's short enough, yet powerful enough and of a .30 caliber which I can list a number of reasons over a 5.56. Or I can simply stay with a 5.56 and hand load heavier bullets for better performance, varying bullet weights and powder charges until I hit that sweet spot of accuracy and performance.

    It just seems to easy and natural to me, as well as appealing to have two or more upper receiver/barrel assemblies that one can apply to the same lower.

    The question is, what can I expect out of a heavier bullet in a .22 centerfire? Is it worth monkeying with? I've seen so many varied results online. Some with great success, some dismal failures, bullets tumbling in flight, hitting paper sideways leaving key-way holes, etc. One argument that stands a winner is simply a longer barrel than 16", for it's widely received that shortening a 5.56 barrel robs it of performance, when it's cartridge was designed originally for a 20" barrel, and shorter lengths really do negatively effect that caliber's performance.

    I would like a longer barrel with a flat-top receiver so we can mount a scope, maybe work up some high accuracy handloads..
     
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  7. BlankinLoud

    BlankinLoud Senior Member

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    @LtDave32 I'm pretty sure the answers to your questions could be found by exploring the varmint hunting community.

    I see a local preference for longer (18-22") barrels on coyote rigs, but I don't know what barrel twists or bullet weights are favored.
     
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  8. Who

    Who are you? Who who who who.... Premium Member

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    When I was a kid.....all we had was 55grain. You whippersnappers with your "rate of twist".

    Back in my day it was all about "rate of fire".


    I once had a nice 26" AR. Flat-top from the days no one made flat-tops, you got a gunsmith to cut a handle off and mount a scope mount. Weaver, none of the fancy Picallily*** crap.

    I got sick of the long barrel, and never had a good place to use it. I had it hacked down to 18". It was nice.

    I sold it just before NY made them illegal. I don't really miss it. But it was nice.



    ***Yes, I know it's not "picallily", but the post is funnier that way.
     
    Last edited: Jul 4, 2017
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  9. KSG_Standard

    KSG_Standard Senior Member

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    I don't have much experience with short barreled rifles or the AR platform, I like bolt actions...that being said, I don't care much for heavier .22 bullets for long range stuff. They are too easily pushed around by the wind. I prefer 6mm, 6.5 or 6.8mm. What are planning to do with the gun when it's built?
     
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  10. smk506

    smk506 Senior Member

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    1/8 FTW.
     
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  11. Frogfur

    Frogfur Senior Member

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    For those that are not clear here, think of a bullet as something like a football in flight kind of thing.

    Dave, using an AR lower as a platform is a good starting point if for no other reason is options.

    As far as barrels go, generally speaking, the heavier the bullet weight, the tighter (faster)twist is necessary to stabilize heavier, longer bullets in flight, and that is why usually a 1:7 or 1:8 is good. Probably the primary reason the military uses 1:7.

    With all these new AR-15, 16" barreled guns out there today, the 1:9(which i like personally)for 55-62gr. are quite good middle ground for a 16" tube weapons.
    However, that is a carbine.

    The other factor to look at is rifling which is very important in any barrel manufacturing process, and varies from manufacture to manufacture. Is it cut rifling, or button rifled.

    Next, are we shooting long range, or shorter ranges ? and, with what bullet weight range do you foresee using mostly ? If we're shooting longer ranges, such as where you are, then I would say something like a 1:7 or perhaps 1:8 twist.

    If you plan on a 20" barrel in 5.56mm I would look at 1:9, and shoot for good load density.
    I am assuming you are in the ranges of 62 to 77gr projectiles and shooting longer ranges.

    I also like the idea of .30 something as well. Especially in the ranges of 110-130gr. But am a solid fan of the . 284 buddy . 7mm-08 perhaps ? Barrel length has accuracy written all over it.

    The key is longer barrels give the powder time to burn and propel the bullet, and generally provide higher velocities.

    Having said that, as pressures behind the bullet diminish as it moves down the barrel Velocities decrease when bore friction and air pressure in front of the bullet will equal the gas pressure behind it, bullet velocity will start to decrease. It is not really clear how much velocity can really be lost per barrel inch. But going from say, 20" to 18" for example doesn't adversely effect accuracy of the rifle.

    As for what you could expect out of a .22 caliber weapon ? It really depends on intended use. Varmiter will tell you hell ya! Me, I damn sure depended on it and I've seen what they do on human targets and it's ugly.
    Sure, its worth messing with if you are considering weight, portability etc.
    Considered 7mm ? Ballistics are better than .30 cap and bullet weights are outstanding.
     
    Last edited: Jul 4, 2017
  12. Who

    Who are you? Who who who who.... Premium Member

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    I'm guessing Lt. already knows a thing or two about the AR platform, and what bullets do.


    Good write-up, Frogfur. Not everyone on MLP is a gun-nerd, so that will help the thread!
     
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  13. SteveC

    SteveC Village Elder V.I.P. Member

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    I shoot a PSA upper, melonite barrel with mid-gas, 1:7, 16" with 55g .223 factory loads for my 3-gun, practical rifle and bullseye competitions. We shoot from 10 yards out to 200 yards. If I do my part, I can get around 2" groups @ 100.
     
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  14. wizard1183

    wizard1183 Premium Member

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    Scar 17 .308/7.62x51 uses 1:12 twist. 16" barrel
     
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  15. Frogfur

    Frogfur Senior Member

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    No question, probably knows allot more about that platform than I do for sure. That's why I always pay attention to what he says.
     
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  16. wizard1183

    wizard1183 Premium Member

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    I bet you could get 1 MOA @ 100 if you reloaded?
     
  17. SteveC

    SteveC Village Elder V.I.P. Member

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    Maybe... but that doesn't really matter to me.

    In 3-gun, all I need are 2 hits in the A-box(es) and to ring the steel at 200 yards. In practical rifle, it's pretty much the same... Double Alpha's at all the distances and while the steel is smaller at 100 yards, clang is clang.

    There are no bonus points for going through the same hole :)

    Bullseye is the only match where I might benefit from a custom load, but there are so many other factors that keep me out of the top-3 there, that reloading is moot.
     
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  18. TheX

    TheX Voice of Reason

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    Which is why I prefer 20" 1/9.
     
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  19. BlankinLoud

    BlankinLoud Senior Member

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    Steve is that an AR only game or do folks with other rifle types participate?
     
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  20. Roberteaux

    Roberteaux Alien Hominid V.I.P. Member

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    It's a twisted topic... :D

    First, a very short and to the point explanation:

    In general, within a caliber class, a longer projectile will call for a tighter twist if the bullet is to remain stable in flight.

    A lighter bullet will be sufficiently stabilized with a looser twist. Again, this is within a caliber class.

    It's really just that.

    And now, for the comprehensive version of this post-- which will be considerably longer than this snippet is.

    --R
     
    Last edited: Jul 4, 2017
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