Bullet Weight
A bullet's mass expressed in grains; heavier-for-caliber bullets raise sectional density and ballistic coefficient but need a faster twist.
Bullet weight is the mass of the projectile measured in grains, the small unit where 7,000 grains make one pound. Within a single caliber a heavier bullet is usually longer, which directly raises its sectional density and tends to lift its ballistic coefficient as well. Higher BC means the bullet sheds velocity and drifts in the wind more slowly, the qualities that matter most at long range.
The catch with heavy bullets is keeping them stable. A longer, heavier-for-caliber bullet needs a faster twist rate to spin it fast enough to fly point-forward, so the heaviest bullets in a caliber often will not stabilize in a slow-twist barrel. Heavier bullets also start slower for a given powder charge and generate more recoil, so choosing a weight is a balance between downrange performance and what the rifle and shooter can actually drive accurately.