This calculation is assuming a 1:12” twist... For quite a while I could not figure out where “720” came from. Turns out it’s simply 12*60, or 12 bullet rotations per 60 seconds for a twist velocity in rpm. Here is an article from accurateshooter.com that breaks down the theory behind twist velocity, and also goes a little deeper into the calcs behind it. https://www.accurateshooter.com/technical-articles/calculating-bullet-rpm-spin-rates-stability/ To the OP: If your looking for optimal spin, you might consider looking at either Greenhill’s or Miller’s optimization equations. They have helped settle a lot of the controversy for me anyway. Not to disregard any of the above comments and suggestions. There is definitely a lot of wisdom in there, far beyond what I have in experience.