BC is about the same as drag coef or friction coef. The higher the number, the more aerodynamic, the lower the worse. It usually runs .15BC for big ole slugs to .5 for .308 ~180gr bullet to .7 or higher for .50 cal500gr bullet. In engineering world. Force=MassXAccel.

Then you get into vel=Vo+At. So you can figure your initial Vo. Ok, getting lost. But you know Force of air against your bullet is slowing you down. And will cause negative acceleration. BC also changes over speed.