The lateral control of a projectile for impacting a non-stationary target is of interest in many applications. Changing the flight trajectory can be achieved using the internal moving parts of the projectile. In this study, three small internal swing masses introduced to the projectile are controlled, and the masses are attached at the end of a massless rod. A mathematical model for the internal gyroscopic rotating disks of this mechanism and its trajectory path is developed. For this mechanism, the equations of motion are developed and solved numerically to simulate the trajectory of the projectile. The projectile is shown to move cyclically about the axis of rotation and deviate from its axis in a relatively even slope. A parametric study is conducted on actuating each mass in sequence or changing the weight of the mass to examine and evaluate the flight trajectory of the projectile. The results from this study show that the projectile could move in a lateral direction in a controlled manner by altering the mass mechanism in a predefined manner. This application may hold merit for controlling the re-entry flight trajectory of air vehicles.