Berger Twist Rate Stability Calculator
The Berger Bullets website has a handy Twist Rate Stability Calculator. It predicts your gyroscopic stabilization factor (SG) using multiple variables: bullet length, bullet weight and velocity. This cool tool will tell you if your bullet will stabilize in your barrel.
CLICK HERE to go to TWIST RATE CALCUATOR PAGE >> How Berger’s Twist Rate Calculator works
It is easy to use the Twist Rate Calculator. Simply enter the bullet DIAMETER (e.g. .264), bullet WEIGHT in grains and bullet overall LENGTH in inches. Berger provides these details on its website for all types of bullets. For other brands, we recommend that you weigh three bullets and measure the length of three of them. The average weight and length of all three should be used. Simply enter your bullet data along with observed Muzzle Velocity and outside Temperature and click “CalculateSG” to calculate bullet stability. You can try different twist rates (and recalculate), until you reach a SG value of 1.4 or higher. Gyroscopic Stability (SG), and Twist Rate
Berger’s Twist Rate Calculator gives a predicted stability value, called “SG” (for “Gyroscopic Sability”). This is the Gyroscopic Stability applied on the bullet by spinning. This number is calculated from the basic equation: (rigidity and spinning mass)/(overturning aerodynamic force). Your bullet will not stabilize if your SG is below 1.0. Your bullet may not stabilize if your SG is between 1.0 and 1. Your bullet should stabilize if your SG is greater than 1.1. However, stabilization may not be sufficient when temperature, altitude or other variables are less than optimal. Berger recommends at least 1.5 SG to break out of the “Marginal stability” zone. His book Applied Ballistics For Long-Range Shooting (3rd Edition) Bryan Litz (Berger Ballistician), recommends a minimum 1.4 SG rating for selecting a barrel twist to fit a particular bullet. This allows you to shoot in a variety of conditions such as higher or lower temperatures or altitudes. EdLongrange has a story idea. We welcome submissions from readers.
