Determing barell twist

Discussion in 'Ammunition & Reloading' started by Tenderribbs, Nov 27, 2012.

  1. Tenderribbs

    Tenderribbs New Member

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    I have this formula to determine best twist rate for bullet. TR= C* D2/lL
    I used 150 for C used .224 for D2 and .790 for L

    I keep getting 84 for answer what am I doing wrong? I'm wanting it for a .224
     
  2. gunnut07

    gunnut07 New Member

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    150 is that bullet weight because there is no 150 gr 224 bullet.
     

  3. The_Kid

    The_Kid New Member

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  4. Tenderribbs

    Tenderribbs New Member

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    Ok didn't know that was the weight , I used 55 for the 150 and still not coming up with a
    Right answer. Here's what I'm doing

    TR =55 * .224(2) divided by .790

    * = multiply. Don't have a multiply sign on keyboard.

    I will use the revised one and see if r helps

    Thanks
     
  5. Tenderribbs

    Tenderribbs New Member

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    Another question thanks for the equation why is bullet weight not in formula?!
     
  6. The_Kid

    The_Kid New Member

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    Because bullet length is what is important.
     
  7. Axxe55

    Axxe55 The Apocalypse Is Coming.....

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    what does the SG stand for? showing a different value based on the bullet material.
     
  8. The_Kid

    The_Kid New Member

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    From that page:
     
  9. Axxe55

    Axxe55 The Apocalypse Is Coming.....

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    thanks. didn't read that far! was thinking it had something to do density.

    how do you find the SG of a particular bullet? is this information readily available?
     
  10. The_Kid

    The_Kid New Member

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    I've seen from 10.9 to 10.7 as the benchmark for jacketed bullets.
    Another example of it being used; JBM Ballistics, Drag/Twist.
     
  11. gunnut07

    gunnut07 New Member

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    What weight bullet are you looking for? 55 gr in a223 needs a 1:12 twist you can go as fast as a 1:8 twist but that is pushing it...
     
  12. Tenderribbs

    Tenderribbs New Member

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    Ion loading up some 60g nosler balistic tip spitzers I'm shooting this bullet from my 1 *8 twist M&P 223 16in barrel. This 24g of varget is nearly filling it up to the neck?? Is it supposed to? Thanks
     
    Last edited: Nov 27, 2012
  13. dustinoif3

    dustinoif3 New Member

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    That's about right. Most of all my loads compress the powder a touch. Except for the garand. It's loaded weak so you hear the powder bouncing around if you shake it. Here is another formula you can try for twist rate/bullet weight calc.

    “military type bullet measuring .647" in length. The bullet diameter is .224", which divided into the length of .647" gives 2.89 calibers long. Dividing 2.89 into 150 yields a figure of 51.90 or an ideal twist rate of one turn in 51.90 calibers. Multiply 51.90 by the bullet diameter (.224") equals one turn in 11.63" for this particular bullet”

    /wa/viewBook?id=411474161