Ballistics Coefficient vs Drag Coefficient for finding Drag Force

[MikeDre]

I wrote a Matlab program for fun to track the trajectory, energy, drop, etc. of a bullet, but I used a C_d instead of BC to determine the Drag Force as this is what I was taught in fluid dynamics classes.

Can anyone educate me on the difference between the two and why one is more correct than the other?

My C_d chosen was .135 for an FMJ .40 SW. Is this totally off?

[tuncas]

Neither is more correct than the other as they are two different things. BC is a function of CD and the two are inversely proportional. Furthermore, CD is dimensionless whereas BC is measured in units of kg/m^2 or lb/in^2.

[MikeDre]

Neither is more correct than the other as they are two different things. BC is a function of CD and the two are inversely proportional. Furthermore, CD is dimensionless whereas BC is measured in units of kg/m^2 or lb/in^2.

I see, so BC is just an easier way to identify a bullet versus using the frontal area, drag coefficient, and mass.

Thanks!

(ie. 1 variable versus 3)