Twist Rate Stability Calculator

Calculate Twist Rate for Bullet Stability



Formula

The formula to calculate the Twist Rate (T) is:

\[ T = \frac{150 \times D}{\sqrt{\frac{L}{D}}} \]

Where:

What is Twist Rate Stability?

Twist rate stability refers to the rotational speed or spin that a firearm’s rifling imparts on a bullet, which is crucial for its stability in flight. The twist rate is usually expressed as a ratio, such as 1:7, meaning the bullet makes one full rotation for every seven inches of barrel length. A bullet needs to be properly stabilized to maintain accuracy over distance, and different bullet lengths and weights require different twist rates for optimal performance.

Example Calculation

Let's assume the following values:

Using the formula to calculate the Twist Rate (T):

\[ T = \frac{150 \times D}{\sqrt{\frac{L}{D}}} = \frac{150 \times 0.308}{\sqrt{\frac{1.1}{0.308}}} \approx 10.9 \]

The Twist Rate (T) is approximately 10.9 inches per rotation.