Drift is a phenomenon that creates a lateral force on a projectile. Its trajectory is deviated in the horizontal plane. This phenomenon is due, seen from the tip of the projectile, to the addition of the rotation velocity along its transverse axis and the precession velocity. The result is that the instantaneous center of precession of the projectile leaves the plane of the trajectory giving a horizontal component to its obliquity. The projectile axis is continuously " oblique " in the horizontal plane and the interaction with the air creates a drift force to the right if the twist is to the right, to the left in the opposite case. The rotation of the axis of the projectile according to the transverse axis exists only on long distance shots, when the curvature of the trajectory is sensitive (important shooting angle). For short distance shots or for tense trajectories, the phenomenon is non-existent