Dear Al, The ballistic coefficient of any given projectile is a three digit decimal number assigned to it by virtue of its shape and weight. It is an indicator of how well the bullet will retain its initial velocity over any distance.
Air is a resistant medium just like water.
The heavier and more aerodynamically efficient bullet will have a higher ballistic coefficient. A light .22 caliber bullet of 55 grains, while having a streamlined and pointed configuration, has a B.C. of .235-.243. A blunt and cylindrical .357 caliber wadcutter has B.C. of .055. Spire point or Spitzer type rifle bullets will always have a higher B.C. than a round nose bullet of identical caliber and weight. Retention of velocity means retention of striking energy when the bullet reaches its target.