Ebook: A new rule for estimating rifling twist an aid to choosing bullets and rifles

Precision Shooting, March, 2005. - 43-48 pp.For a bullet to fly point-forward, it must spin fast enough to be stable. For stability, the "gyroscopic stability factor" s, which depends on the spin rate, must be greater than.
1.0. Because the spin in flight declines considerably more slowly than the forward velocity, the bullet's stability factor increases as it flies downrange, and it actually becomes more stable. Consequently, the stability factor at the muzzle is the most significant. Since the spin rate at the muzzle depends on rifling twist, twist is an important part of the stability factor.Contents:.
Introduction.
The New Rule for Twist and Stability Factor.
Sample Calculations.
Where Does Our Rule Come From?
Effects of Velocity (Mach Number), Temperature, and Pressure.
Technical Notes.