What he said. A high velocity rifle round, especially a .50 Browning, doesn't just poke a hole in a person for the same reason thowing a rock in a pond doesn't just make a rock-shaped hole in the water. It makes a big splash, depending on a number of factors (shape, angle, velocity, mass, etc.). When that big splash is your insides, you're having a bad day.
Kinetic energy can cause significant wounding in of itself, if it's applied correctly.