Determing barell twist
 

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

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

I'd go here and use the revised formula.

A Calculator for Barrel Twist Rate

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

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

Because bullet length is what is important.

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

From that page:

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?

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.