Retained Velocity
The speed a bullet still carries downrange, which determines its remaining energy and whether it stays supersonic to the target.
Retained velocity is the velocity a bullet still has at a given distance, after drag has bled off part of its launch speed. How much it keeps depends heavily on the ballistic coefficient: a sleeker, higher-BC bullet sheds speed more slowly and arrives downrange carrying a larger share of its original velocity.
This figure drives two things that matter at range. Retained velocity sets the kinetic energy available at the target, which is decisive for hunting and terminal performance. It also decides whether the bullet remains supersonic at distance, because once retained velocity falls toward the speed of sound the trajectory becomes much harder to predict.