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Thread: Twist!

  1. #1
    GunLoad Trainee duncaninfrance's Avatar
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    Default Twist!

    Is there such a thing as a chart or series of charts that will give the correct rifling twist for various calibers and bullet weights?
    Duncan.
    "I don't drink water, fish fornicate in it" W.C.Fields

  2. #2
    Dogs Like Him versifier's Avatar
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    There is a formula, based on the Length (bearing surface) of the bullet.

    Proper Twist:
    150* x caliber diameter in inches x (cal diameter/bullet length)
    *For velocities over 3000fps use 170, and under 2500 use 130

    Proper Bullet Length:
    150 x cal diameter x (cal diameter/twist in inches)

    Bear in mind that this is a general guideline. It's usually pretty good, but I can't tell you how many times I have seen a barrel stabilize a bullet that is much too long or too short by the book. Neither rifles nor bullets can read.

    The bottom line is you have to actually shoot it to get that particular barrel's opinion. Most recently, I advised a shooter that his .223 with a 1/10 twist would probably not stabilize a 70gr bullet. Usually they keyhole and pattern like a shotgun. He proceeded to shoot a one hole group with the rifle at 100yds with his handloads. His comment was "I'd read that, too. Don't tell my rifle, OK?"
    "Stand your ground.
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  3. #3
    runfiverun runfiverun's Avatar
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    Default

    generally the longer [heavier] your bullet, the faster your twist rate.
    the greenhill formula above is pretty close though.
    remember it is just a guidline,and you can go over or under what it says.
    mainly cause, guns are just like that. some will some won't.

  4. #4
    GunLoad Trainee duncaninfrance's Avatar
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    Thanks guys.
    I was given this ling by someone on another forum which is very good.

    http://www.riflebarrels.com/products...wist_rates.htm
    Duncan.
    "I don't drink water, fish fornicate in it" W.C.Fields

  5. #5
    swamp
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    Your link doesn't work.

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    GunLoad Trainee Ed Barrett's Avatar
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    Default

    If you look at the tables at the end of each section of "Cartridges of the World" they list the twist rates for each cartridge.
    Ed Barrett
    AKA; elbStJoeMO

  7. #7

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    Good morning
    The NRA Fact Book has a section on ballistics,stability, rotation... does get real DEEP... simple easy and I enjoy the book.
    Mike in Peru

  8. #8
    GunLoad Trainee
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    Quote Originally Posted by duncaninfrance View Post
    Is there such a thing as a chart or series of charts that will give the correct rifling twist for various calibers and bullet weights?

    Here's a few threads you can follow:

    http://www.riflebarrels.com/products...wist_rates.htm

    http://www.nfa.ca/content/view/129/197/

    http://www.montanabulletworks.com/wst_page11.html

    Mike

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