This Twist Calculator Calculator is a tool for determining the Gyroscopic Stability (GS) of your bullet and is based on the Don Miller twist rule. (Learn More). This calculator is used to find the optimal twist rate for your bullet. This is a general information calculator and there may be additional parameters that can have slight effects.

    Input Suggested Twist
Bullet Length   in INCHES : REVOLUTION*
    *Round Down To Closest Half Twist
Bullet Diameter   in
Muzzle Velocity   fps

Bullet SG  
Bullet SG Values:


11.3 Lead
10.0 Jacketed
8.9 copper
8.5 brass
7.8 steel