Which guns (real guns... not toy guns) shoot bullets that I can stop with my body?

Here's a fun math/science question that's slightly morbid... let's say someone was going to get shot by a gun and I wanted to save their life by jumping in the path of the bullet. Which types of guns can I "safely" jump in front of to ensure that it doesnt come out my back side and the victim. You wouldn't want to jump in the path of a bullet that was going to go straight through you and reach the target victim anyways right? That would just be wasting your life. Now I realize that there are many variables in this equation such as the thickness of the jumping person, the location on the body, the composition of the body m, the distance between the gun and the body, the type of gun... but is there a way to either generalize the answer or give an equation in which we could input our own data and find out? If the nerds can't answer this, I'm sure there are some gun freaks out there that can. Thanks.