What is the unit of the drag coefficient cD and what is the connection between cD and the projectile caliber?
The drag coefficient is a dimensionless number (in the area of 0.1 – 1) and depends on Mach number, Reynolds Number, Froude number,… The drag coefficient is usually measured by Doppler Radar or other velocity loss measurements. There is no simple relationship between bullet geometry (length, diameter, shape) and cD. Q: Where might I find more information about estimating CM (overturning moment coefficient) for various shaped bullets, primarily boat tail and flat base match bullets. A: All the aerodynamic coefficients are usually hard to obtain. Military research institutes measure them but only for military bullets. Almost no data is available for bullets from the civilian market. There is some (expensive) software available which estimates the aerodynamic coefficients from bullet geometry. Q: If a bullet is fired vertically from a rifle, what will its terminal velocity be if it strikes the top of someones head on its way back down? A: This question is hard to answer in general. The
