BC takes into account the shape of the ideal and its calculation does involve the bullet's SD as well. SD takes into account the bullet's weight and diameter, and both these are finite. Once the bullet starts to penetrate, the bullet's frontal diameter may be unpredictable and it may lose mass, but in bullet's of similar construction, sectional density can still be valid. Because bullets of a fixed bore diameter and construction must grow in length if they grow in mass, and because a bullet's sectional density it directly proportional to both its mass and diameter, longer and heavier for caliber projectiles will tend to have higher sectional densities. In bullets of similar construction impacting a similar target at proportionally similar velocities, and everything else being equal, expansion should be controlled to preserve a similar amount of the shank. This section will still be longer on the heavier bullet, so even after and during expansion, the longer bullet with its higher SD will still be longer, which at least in theory should help in straight line penetration. This means that in similar construction a 150 gr .284 cal should be expected to penetrate farther than a 150 gr .30 caliber projectile and a 160 gr .284 cal projectile should be expected to penetrate farther than the 150 gr projectiles. This is why I probably will end up sticking with the 160 gr Accubonds in the long run.
