I'm no expert, but I would think speed and what happens when the bullet hits flesh/bone would be the most important factors. A FMJ does little damage to the surrounding area regardless of weight or speed, but it has to at least have enough speed to penetrate one side of the target. If it has enough speed to go through the target thats ok. How the bullet reacts is probably most important. Does it mushroom, fall apart, etc... There is a company making a bullet that I saw on TV that will shoot through a metal plate, 1/4' thick, I think and turn into a powder that completely obliterates a ham. They claim there is nothing coming out the other side of the ham, if I remember correctly. Complete 100 percent meat loss on the ham. So, what the bullet does once it penetrates the target probably has the most to do with the damage.
