Twist Rate Calculator
Free calculate twist rate for rifled barrels. determine the rate of rotation required to stabilize projectiles based on bullet characteristics.
Input Parameters
e.g., .308, .223, .50
Recommended: 1.3-2.0 (1.5 typical)
Results
Enter parameters to calculate twist rate
Twist Rate Formula (Greenhill)
Twist Rate
T = (150 × d²) / L
Where d = diameter, L = length (simplified)
Miller Formula
T = (30 × m) / (t × d² × (1 + L²))
More accurate for high velocities
Stability Factor
S = (30 × m) / (t² × d³ × L × (1 + L²))
Where m = mass, t = twist rate
Common Twist Rates
- • .223 Rem: 1:7 to 1:12
- • .308 Win: 1:10 to 1:12
- • .50 BMG: 1:15
- • Faster = shorter bullets