Often a heavier bullet will strike higher on the target than a lighter one. This is because the heavier bullet develops a greater recoil impulse than a ligher one, and, as it travells more slowly to the muzzle, the barrel has a longer time in which to rise in recoil, so that when the bullet exits the muzzle, the bore is pointing up more in relation to the target. However, in additon to the gross movement of the entire barrel, a barrel generaters high-speed vibrationsdue to the energy released on firing, so that the muzzle actually "flops around" some before the bullet exits. So it is POSSIBLE for the muzzle to be pointing almost anywhere in relation to the target when the bullet does exit. This vibration can cancel the rise of the bore, and make the bullet gostraight, up, or down on the target.

Short, stiff barrels are more likely to throw heavier bullets higher and with less barrel vibration than long, thin, whippy ones. These tendencies are even more in evidence in handguns.