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Twist Rate Calculator
Calculate barrel twist rate for rifle accuracy
📖 Twist Rate
Twist rate is the distance a bullet travels in the barrel for one complete rotation. Proper twist rate stabilizes the bullet for accurate flight. It's expressed as 1:X (e.g., 1:9 means one rotation per 9 inches).
📊 Result
💡 Tips & Information
- Twist rate is expressed as 1:X (one rotation per X inches)
- Formula uses Greenhill formula: T = (150 × D²) / L for velocities above 2800 fps
- Longer, heavier bullets require faster twist rates
- Too slow twist = unstable bullet, too fast = excessive wear
- Common twist rates: 1:7 (fast), 1:9 (medium), 1:12 (slow)