I have an argument with a fellow Airman about this. Which would do more damage at point blank range (within 25 ft): a 5.56mm NATO (M855) fired from an Colt M4 or a 9X19mm JHP (hollowpoint) fired from a Beretta M9? Both are fired into the sternum and no body armor is used. He says the 9mm would because although it is a pistol round, the hollowpoint is designed to "spread" on impact, thus imparting more energy on the body and the 5.56mm would just whiz through with minimal damage. I say its the 5.56mm because hollowpoint or not, the round hitting the sternum at 3100 f.p.s. is going to cause the bullet and breastplate to shatter, forcing debris into the chest with plenty of velocity. Any help would be appreciated.