I personally think that the first blood rule is unrealistic and far too deadly.
So's real life combat...
If you get shot in the chest, you're in critical condition - and most likely have what's called a Sucking Chest Wound.
It sucks, so I've been told.
Once your lung collapses, you're on a countdown. That countdown is how long it takes for your body to run out of oxygen.
Now if you don't get medical attention...
On the other hand, if that chest wound hits your heart, you're probably done before you can get to a hospital.
A head wound that penetrates the skull, well, if you don't end up dead, you're a vegetable.
I hear stomach wounds are kinda nasty - but could take weeks to kill you.
If you get shot anywhere else, it just depends if it hits a good sized artery/vein or not.
That's just what I remember from U.S. Navy Boot Camp GunShot Wound First Aid Training.
Any head or chest wound that penetrates the bone has a pretty good chance of killing you. Everything else is a good story to tell your grandkids. They teach police to fire at center of body mass - smack dab in the middle of the chest. Any professional would do the same - unless it's a sniper (who aim for the back of the skull). It's the amatures that are unpredictable and shoot you in the foot.
I think that's why that first blood rule applies - if your don't get killed right off the bat, the person shooting at you probably sucks. hehe
Dameon