EDgun West's Airgun Calculators

Twist Rate Calculator

The twist rate calculator will assist you in determining the stability of a bullet when fired from a particular rifled barrel. It has been long-established that the bullet should spin or rotate along the longitudinal axis to c long travel distances while maintaining stability. This spin on a bullet is induced by introducing grooves in the barrel. The bullet stability is varied with different barrels and is estimated using the Greenhill formula or the Miller twist rule.