The original ball ammo provided to the military was actually very efficient against a human. Ball ammo has a tendency to yaw upon impact. While this limits penetration, it does cause massive wounding. Not good for hunting but definitely good in a firefight. Hunting ammunition in .223/5.56 has really progressed and is designed to penetrate and have controlled expansion. While it is far from a first choice for whitetail sized game, in qualified hands it is an effective cartridge with todays advanced bullet designs. If it can kill a 150-300 pound wild hog, and I know for a fact it can because I have dropped quite a few with mine, then it can take a much easier to penetrate whitetail deer. But you are limited in both range and shot placement which is why I stated it should be used only by qualified individuals with excellent marksmanship skills as well as patience to wait for proper shot presentation.