There is a lot of good thoughts here. The way I always looked at round balls for hunting for example the .50 caliber. If you knock a 1/2 inch hole through somethings heart and lungs, I can almost guarantee they will not live through the experience. A deer is a thin skinned animal. It would not take a lot of energy to punch through the skin and through the organs.
The other thing people forget about round balls are once they enter an animals body, there is no telling what will happen next. This year I shot a deer with a .54 caliber roundball hitting that big rib behind the shoulder first. The ball busted the rib, pushed that into the lungs, then followed the rib up, knocking out a chunk of spine. That equals dead deer.
A funny story. Years ago during our modern season, I was hunting with a friend in some hardwoods. I pulled my .54 caliber Renegade out of the truck and he began teasing about how I could not afford a modern gun. He then asked why I brought a single shot when I had so many tags to fill. I told him not to worry about me...
I took my stand and my friend was hardly over the hill when in came two deer. I took out my binoculars and checked them out. One was a nice little buck. I took my eyes off them and put the glasses away, then repositioned and shot that buck at 80 yards. The .530 round ball with 80 grains of Pyrodex RS went through that deer and killed a doe that was standing 20 feet behind the first one that I did not see... I had more then enough tags to cover the mistake, but that just tells you what a round ball will do.
My friend heard the shot and came back to check on me. He heard THE SHOT and screamed, "what did you get, buck or doe?" My answer was, "yes." When he saw the two deer, he swore that I did it on purpose. I then told him to fire off my muzzleloader as I did not need it loaded (I had my hands full cleaning deer). He was a little scared of it. I told him it would not knock him over. He shot it and was amazed at how accurate it was.
After getting them out, I went to town to register them, he went to the local tavern and told everyone I was too cheap to waste two bullets and waited until I could gang shoot them... :haha: The next year he had a CVA .50 caliber Hawkins...