I know anatomy well enough to know that a hole through your upper middle is going to be bad news. Two or three holes is even worse.
Most of your important bits are covered by the rib cage, so - taking into account the fact that your groups are probably going to be much larger in a gunfight than they are on the range - between the pecs seems like a pretty effective place to aim.
COM north I guess?
I don't think anyone was actually suggesting it, but aiming for specific organs seems unrealistic. It works for hunting because you generally have time, and don't want to ruin meat, but if you have enough time to set up a perfect insta-kill shot on a human you probably have better options.
si vis pacem para bellum