The overturning moment
moment coefficient, cM(B, Ma, Re, d)
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 MW is called
overturning moment or yawing moment (see figure).
For spin-stabilized projectiles MW tends to increase
the yaw angle and destabilizes the bullet. In the absence of spin, the
moment would cause the bullet to tumble.
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