Carl Levitan had the best advice, I think. Go for the gut.
The digestive system is the ONLY closed system in the body (meaning that it functions without directly contacting other organs). The mouth, esophagus, stomach and intestine are a basic straight line running in and out of the body. The reason that the digestive tract is closed is the manufacture and use of hydrochloric acid in your stomach. It's used to digest your food, and your body makes it constantly. It also makes mucus to protect the stomach lining from the acid's effects. If you don't have enough mucus made for the amount of acid you produce, you end up with ulcers, where the stomach acid starts eating holes in your stomach wall.
Ever have heart burn? REALLY bad heart burn? That is caused by the gas from the food you ate making the stomach acid rise to the point where it contacts your cardiac sphincter, the entrance to the stomach just below the heart. Anyone who's had it can tell you that it isn't fun. (BTW, if you ever get bad heartburn again, don't use TUMS, use Gas-X. The simethicone in Gas-X will disperse the gas in your stomach and cause the acid level to drop.)
When a bullet is fired into the stomach, it rips a hole in the stomach wall allowing the hydrochloric acid to leak out into the peritoneal cavity, where all your other organs are. The acid burns like crazy, and your other organs aren't designed to handle it, so they shut down. It continues to flow into the peritoneal cavity damaging everything it touches, and can lead to Sepsis and Peritonitis (infections) both of which can be fatal.
When Carl described people saying that their "insides were on fire", what they were feeling was the stomach acid burning everything as it leaked out and went along its merry way. Make no mistake, a gut shot IS fatal if not tended to by proper medical professionals. Blood and acid do not like each other, and acid usually wins. Sooner or later acid will get in the bloodstream, and then the party is OVER.
If I ever have to deal with a BG and all I have is my NAA Pug, I'll be shooting four shots at his gut and one at his throat.