🎯 Twist Rate Calculator
Calculate a projectile’s spin rate from muzzle velocity and barrel twist rate.
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Bullet Spin Rate from Twist Rate
Rifle barrels are rifled with spiral grooves that spin the bullet for gyroscopic stability. Given the twist rate (expressed as one full turn per N inches of barrel) and the muzzle velocity, the resulting spin rate is RPM = (velocity in fps × 720) ÷ twist rate in inches. The constant 720 arises from converting feet-per-second into inches-per-minute and accounting for one revolution per twist length.
A “faster” twist (smaller N, like 1:8) spins the bullet more per unit of travel than a “slower” twist (larger N, like 1:12), which matters for stabilizing longer, heavier bullets. This is a standard ballistics reference calculation for general educational purposes.
Last reviewed August 2026