@ DRMMR02
Question: If most standard pistol rounds don't even go through the first target, how much force does a bullet really have when it does get all the way through? This may be a stupid question, but if we're concerend with a bullet not even going into the first thing it hits far enough to stop it, how much damaging potential does it have after it does get all the way through?
I think the only reasonable issue to discuss here is the potential for damage to the surroundings, should the shooter miss the intended target.
But...to satisfy your curiosity there are many cases in the literature where a single shot has damaged two individuals.
In a study that I conducted in Johannesburg in 2002, I took a sample of 150 gunshot victims and determined whether they had penetrating or perforating injuries. (Many people don't know the difference between penetration and perforation. In penetration, all of the projectile components remain in the target, in perforation a portion of the projectile or the whole projectile exits the target).
Here is what I found:
Note that there was one confirmed .303 rifle injury and one confirmed shotgun injury and there are two cases where I can't be certain whether a rifle or a handgun was used, but the majority of these cases involved handguns.
So, certainly, a very significant number of shootings are perforating in nature. Whether the exiting projectile has enough energy to damage a second person depends on too many variables for me to offer a worthwhile answer. My opinion is that you should assume (in most cases) that when you pull the trigger, a person standing directly behind the target will be hit by your bullet too.
There is another thing you have to understand: you can have a perforating injury even if the projectile does not remain intact. Look at these figures for the detection of projectile fragments in those 150 cases:
Note that there were fewer cases where projectiles were not found in the patient's clothing or detected on X-ray, than there were cases where the victim sustained a perforating injury. This means that in at least a few cases there was a perforating injury but at least some of the projectile components were retained in the victim's body or in his clothing. Therefore you have to consider the potential variable of a reduced mass projectile exiting the first target and striking the second.