Step 1. Place the gun in the cradle. Adjust the gun's position so that the bubble level returns to reading level, indicating that the gun's balance point matches the cradle's balance point.
Step 2. Twist the gun and cradle gently and release to produce a slight horizontal oscillation. At a conveniently determined point in the swing, begin timing with a stop watch. A period consists of one full swing back and forth. Time at least ten oscillations, and stop timing on an exact number on periods.
Step 3. Divide the total time by the number of oscillations timed to determine the average period.
Step 4. Use the average period, the torsional stiffness and pendulum's MOI (from the calibration) to calculate the gun's MOI.
