The overturning moment

Abbreviations

c_M	Overturning moment coefficient, c_M(B, Ma, Re, d)
e_W	Unit vector
M_W	Overturning moment

More Abbreviations

Explanation

The point of the longitudinal axis, at which the resulting wind force F₁ appears to attack is called the centre of pressure CPW of the wind force, which, for spin-stabilized bullets is located ahead of the CG. As the flow field varies, the location of the CPW varies as a function of the Mach number. Due to the non-coincidence of the CG and the CPW, a moment is associated with the wind force. This moment M_W is called overturning moment or yawing moment (see figure

). For spin-stabilized projectiles M_W tends to increase the yaw angle and destabilizes the bullet. In the absence of spin, the moment would cause the bullet to tumble.