There are a number of ways in which “ballistic coefficient” can be defined, some of which are more technical than is necessary to understand and use the concept. Quite simply, the ballistic coefficient (BC) of a bullet is a number that represents how efficiently and cleanly that bullet flies through the air. Put another way, the BC expresses how well the bullet overcomes air resistance and resists deceleration in flight. BC is thus related to drag. The higher the BC of a projectile, the less aerodynamic drag it has, and the more velocity it retains downrange.
BC is related to bullet shape, weight and diameter. We don’t need to know the actual formula; we just need to remember two things. First, BC is highly dependent upon bullet shape. In any given caliber, projectiles with long, spiky noses (ogives) and boattail bases will have higher BCs than bullets having blunt noses and flat bases. And second, larger-diameter bullets can have higher practical BCs than smaller-diameter projectiles. The emphasis here is on the word “practical.” Many match bullets for the .50BMG, for example, have BCs approaching or exceeding 1.00. In theory, it would be possible to design a .22-caliber bullet with a BC of 1.00, but it would be absurdly long and heavy, and would require a ridiculously fast barrel twist, and even then it would be too unstable in flight to be accurate over any reasonable distance.
There are a number of ways in which “ballistic coefficient” can be defined, some of…
by Chuck Taylor / Jun 21, 2008