Taz -- I forgot to ask the bullet length, so try this formula--
(180 x bullet dia x bullet dia)/ bullet length = rate of spin. If your velocity is below 2800 fps, use 150 instead of 180 as your constant. CJ
What formula do you use to determine your first number ( 180 or 150 ) versus Velocity?
I was thinking that with the formula you gave, I might be able to reverse it when working up new loads. With a known twist, it might help me look for a specific window of velocity for best bullet performance. But I can't find how your beginning numbers relate to the bullets speed.
Tim-- Good Question-- I pulled it off of one of the ballistics sites and I don't remember which one. I'll try to find it and get back to you. I don't remember seeing the formula, just the numbers given as constants. I'll try to look it up tonight. Chris