Ballistic Coefficient
Also: BC · G1 BC · G7 BC
A single number that describes how well a bullet resists air drag. Higher BC means a flatter trajectory and less wind drift downrange.
BC compares a bullet’s flight characteristics to a reference projectile. Two reference models matter in practice: G1 (a flat-base reference) and G7 (a boat-tail reference). For modern boat-tail rifle bullets, G7 numbers track reality more closely, while G1 figures tend to read higher than the bullet actually delivers.
A G7 of 0.300 is excellent for a 6.5mm bullet, while a G7 of 0.200 sits toward the modest end for that caliber. The number isn’t constant across the bullet’s flight, since published BCs assume a velocity band and average across it.