# Determing barell twist

1. ### TenderribbsNew 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. ### gunnut07New Member

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

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4. ### TenderribbsNew 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. ### TenderribbsNew Member

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

6. ### The_KidNew Member

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Because bullet length is what is important.

7. ### Axxe55The Apocalypse Is Coming.....

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

8. ### The_KidNew Member

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From that page:

9. ### Axxe55The 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_KidNew 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. ### gunnut07New 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. ### TenderribbsNew 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. ### dustinoif3New 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.

&ldquo;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&rdquo;

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