Ballistic Coefficient (BC)
A number describing how well a bullet resists air drag — higher BC means a flatter trajectory and less wind drift.
The ballistic coefficient quantifies how aerodynamic a bullet is relative to a standard reference projectile. A higher BC means the bullet sheds velocity more slowly, so it drops less, drifts less in wind, and retains more energy downrange. Long, heavy, streamlined bullets (boat-tail, polymer-tip 'match' bullets) have higher BCs than short, blunt ones.
BC matters most at distance. Up close, almost anything shoots flat; past a few hundred yards, a high-BC bullet dramatically reduces how much you must hold or dial and how much the wind pushes you. It's one of the key inputs — along with muzzle velocity — that a ballistic calculator uses to build a trajectory.