Bc is a measure of a bullets resistance to drag. The less drag, the less outside (wind-air) effect. If you start two bullets, one a 220 gr roundnose and the other a 210 gr berger vld at the same speed, the berger will waste it down range. Now give the round nose a 300 fps headstart....the berger will pass it in a couple hundred yards.....all because it is "slicker". The downside to high bc bullets, is they tend to be long and slow twist guns will not always stabilize them.