Barrel twist

[GregLaROCHE]

Is there any kind of formula for calculating the best twist rate? Caliber, boolit weight, load, ft/sec, barrel length? Or is it just what has been known to preform well?
Thanks

[M-Tecs]

http://kwk.us/twist.html

https://firearmshistory.blogspot.com/2012/11/how-to-calculate-twist-rate-i.html

https://www.vcalc.com/wiki/AndrewBudd/Greenhill+Formula+for+Optimal+Rifling+Twist+Rate

https://ebrammo.com/info-tools/greenhill-formula-for-rifling-twists

[bigbore52]

Greg,

try Greenhill's ready made formula here :
https://www.vcalc.com/wiki/AndrewBudd/Greenhill+Formula+for+Optimal+Rifling+Twist+Rate

I've not used that link but the following Wiki link has the formula if you want to do it yourself:
https://en.wikipedia.org/wiki/Alfred_George_Greenhill

....interesting most formulae such as Greenhill's rely on a constant and are limited to velocities sub 2400fps - I prefer to use Millers formula (based on Greenhills') that accounts for a greater number of variables including copper jacketed etc...
His formula called the Miller Twist Rule can be found here

https://en.wikipedia.org/wiki/Miller_twist_rule

Hope they help.....