One thing that matters as well is not just bullet mass and velocity, but also the cross section, since it determines how much of the bullet’s energy will be dissipated in the target. The fastest bullet will not have much stopping power if it just enters the target and leaves it again still with most of it’s kinetic energy. Hunters like to use soft point or hollow point bullets, which will mushroom inside the target, dramatically increasing the cross section. These bullets are banned for military use due to Geneva convention, like Dumdum bullets, though some modern bullets, which topple inside the targets have a similar effect.
Jan