BC honestly is all kind of relative. The BC's published on every box of bullets are listed at a specific velocity. If you do not obtain that velocity the BC of the bullet will not be as high. Like I have said above everything I know about long range shooting has been self taught and you may know a hell of a lot more than myself but I don't see how much energy the projectile hits with (force) has at any impact on the projectiles BC during its flight.
Target bullets have a different jacket that makes them not proper for hunting, i.e. They won't expand.