[Michael Hill]

I should also note that 120000 is a rather high Reynolds number. 10 m/s is extremely fast for this kind of game. When I was doing the calculations, I was still stuck in Aim High mode, but looking back, Re should probably be about half that, and a C_D of 0.5 should be a decent estimation.

If you want an even better estimation, you can use C_D = 0.09015*log(Re) + 0.06924

Where:
C_D = Drag Coefficient
Re = Reynolds Number = rho*V*D/mu
rho = Density of Air
V = Velocity
D = Diameter of Ball
mu = Dynamic Viscosity

This is fine as long as the Reynolds number stays below about 8*10^4