Air resistance on the rifle range

 

Having done yesterday's calculation, I realised that I had neglected air resistance. I discovered that there is a complicated discipline called external ballistics but I've opted to try a simpler drag coefficient that I might understand. If viscous drag = 1/2 x density x velocity-squared x drag coefficient x cross-sectional area then if I use a drag coefficient of 0.3 (suggestion is that a bullet would be between 0.1 and 0.3) then I'd get drag force = 1/2 x 1.2 x 745^2 x 0.3 x 5 x 10^-5 = 4.6 Newtons. I calculated a cross-sectional area based on the .303 diameter bullet. More thinking to be done because it depends on speed so will decrease in size as the air resistance slows the bullet. It seems in the full analysis, they use something called ballistic coefficient instead of drag coefficient which seems to incorporate mass as well.