1. What is Bullet RPM?

Bullet RPM (Revolutions Per Minute) measures how fast a bullet spins as it exits the barrel. This spin stabilizes the bullet in flight, improving accuracy. The spin rate is determined by the muzzle velocity and the barrel's twist rate.

2. How Does the Calculator Work?

The calculator uses the RPM equation:

Where:

• \( Muzzle\ Velocity \) — Bullet speed at muzzle exit (feet per second)
• \( Twist\ Rate \) — Barrel twist rate (inches per complete turn)
• 720 — Conversion factor (60 seconds × 12 inches)

Explanation: The equation calculates how many complete rotations the bullet makes each minute based on its speed and the barrel's twist rate.

3. Importance of RPM Calculation

Details: Proper bullet spin is crucial for accuracy. Too little spin causes instability, while excessive spin can cause jacket separation or reduced accuracy. Most bullets require 120,000-300,000 RPM for optimal stability.

4. Using the Calculator

Tips: Enter muzzle velocity in feet per second and twist rate in inches per turn. Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why is bullet spin important?
A: Spin stabilizes the bullet via gyroscopic effect, preventing tumbling and maintaining accuracy over distance.

Q2: What's a typical twist rate for rifles?
A: Common twist rates range from 1:7" (fast) to 1:14" (slow), depending on bullet weight and caliber.

Q3: Can RPM be too high?
A: Yes, extremely high RPM can cause bullet jackets to separate from cores due to centrifugal force.

Q4: How does bullet length affect required spin?
A: Longer bullets generally require faster twist rates (more spin) for stabilization.

Q5: Does temperature affect RPM?
A: Indirectly - temperature changes muzzle velocity, which affects RPM. Hotter loads typically produce higher RPM.