Bullet Type
    Bullet type can have a significant effect on leathality, contingient upon some other factors. The most important of these factors is that the bullet be given enough velocity to perform properly, and that it hold this velocity until it reaches the target. Terminal velocity is probably the most important factor in the performance of a particular bullet design. The magical number seems to be 1100fps. The velocity of sound in air is approximately 1130 feet/sec. or 770 miles per hour at room temperature of 70 deg F. This is an important velocity, because it greatly affects the properties of projectiles, in a couple of ways. 

hollow point
black talon, and other special designs
armour piercing.

Bullet type can be a significant factor, if certain variables are properly considered. The two most important are velocity, and         Also important, but beyond the control of the shooter, is the density of the target.