i know a bit about ballistics. it's more practical knowledge. i've seen enough gunshot wounds to pick up something here and there. the high velocity ones wreak havoc inside. the more usual 9mm doesn't compare but a well placed shot is still devastating. and then you get the exceptions. ricochet shots can be confusing. they tend to take strange paths through the body, sometimes following dissection planes (like surgeons) and causing less damage than you'd expect. and then you get the tumbler.
i did a tumbler recently. it wasn't a particularly high velocity projectile. the bullet didn't even make it through the patient. the entrance wound was just below the rib edge to the left of the midline. i could feel the bullet under the skin just below the right arm (bullets that are palpable just below the skin usually mean deflected bullets, either before penetration, like a ricochet, or in the body by hitting bone). he also had a hemothorax on the right. he was sinking fast so we got him to theater without too much delay. the intercostal drain delivered a good liter and a half, but then dried up. laparotomy was the first order of business.
despite the normal entrance wound and the relative low velocity, the damage inside was impressive. there were two 5cm holes in the stomach. the bullet then continued into the liver, causing a massive tear where it entered and an equally impressive one on the dome where it exited on it's way through the diaphragm into the chest. the hemothorax (bleeding in the chest) was actually from the liver.
so, although the bullet was small as bullets go and also not of the fast variety, the fact that it was no longer stable in it's trajectory meant that it caused a relatively large amount of damage. imagine it tumbling as it travels through its victim. the amount of energy parted to the tissue is considerably more than it would be if the projectile just behaved and followed a straight line.
the other interesting thing with this case is that, for a change, i did in fact follow the advice of countless hollywood productions and i removed the bullet. (usually it is not necessary to remove a bullet, with certain exceptions of course. it is not the presence of the bullet that causes the damage, as hollywood would have us believe, but the movement of the bullet through tissue at the moment of the shot)