3-131. The lands and grooves in the bore of the rifle impart a rotational motion to the bullet about its own axis. This rotational motion causes the projectile (as it travels through the air) to shift in the direction of rotation (in almost all cases to the right). This motion causes a drift that is caused by air resistance. A spinning projectile behaves precisely like a gyroscope. Pressure applied to the front of the projectile (air resistance) retards its forward motion but does not significantly upset its stability. However, upward pressure applied to the underside of the projectile (due to its downward travel caused by gravity) causes it to drift in the direction of spin. This drift is relatively insignificant at all but the greatest ranges (more than 1,000 yards).