Your question reminds me of two murders I helped investigate while in Vietnam with the Criminal Investigation Division.
The first involved a soldier drinking on guard duty. The Sargent of the Guard caught him. The drunk fired a single round from his M-16 at the Sargent. The 5.56 mm round struck the victim on the collar bone of his right shoulder. It shattered the bone and ricocheted downwards and to the left through the torso of the man's body, coming to rest just above his left hip. The bullet tumbled and fragmented as it went through the man's body, leaving a devastating wound that the sargent did not survive. A .308 round would have just punched through the collar bone and shoulder, leaving the Sargent wounded but alive.
The second case involved a young MP working a traffic control point. He was holding traffic as a long convoy was passing through. A Sargent in one of the stopped vehicles became angry at having to wait so long. According to numerous witnesses he approached the MP, shouting and cursing, demanding that the MP stop the convoy so he could get by. The MP told him to get back in his truck. Witnesses said that the Sargent , a short, fat, 280 pound man, pushed the MP. The MP responded by pulling his .45 auto and again ordering the man back to his truck. The Sargent cursed and said, "Gimme that f*****g gun" and reached for the weapon. Witnesses told me the MP fired two rounds into the Sargent . The Sargent , looked surprised, cursed again, took another step towards the MP, and the MP fired two more rounds. The man reached out with both arms took another step and the MP fired the remaining three rounds into him. Witnesses told me that Sargent stood for a few more seconds and finally fell to the ground. I was assigned to witness the autopsy. All of the rounds were center of mass hits. Five of the rounds had hit the man just below the sternum, one of them poked a hole in the bottom of the heart. The other three were in the chest, two had punctured the left lung and one had gone through the esophagus. None of the rounds fully penetrated the body, all the bullets were recovered. None of them were mushroomed, but were deformed.
The .223 certainly is a man stopper. The bullet will do terrible damage to the body. The human body, on the other hand, can absorb an awful lot of punishment. If I had to chose which round to be hit by; I think my chances of surviving the hit would be better with the .45