The Magnus force, which applies at its centre of pressure CPM can be
substituted by a force of the same magnitude and direction, which applies
at the CG, plus a moment, which is said to be the Magnus moment
MM 
This moment tries to rotate the bullet about an axis, perpendicular to
the longitudinal axis of the bullet.
However, the gyroscopic effect also applies for the Magnus moment and the bulletīs axis will be shifted into the direction of the moment. Thus, as far as the conditions of the figure above are valid, the Magnus moment will have a stabilizing effect as it tends to decrease the angle of yaw d.
It can be easily shown that this is only true, if the centre of pressure of the Magnus force CPM is located behind the CG. The Magnus force destabilizes the bullet and increases the angle of yaw, if its centre of pressure is located ahead of the CG, which may come true in a specific velocity regime.
