My good friend who barely knows how to use a computer only uses .223 for deer. His family owns two rifles: a ruger .22LR and a Ruger .223. he and his two sons shoot only these two rifles. He's a very, very, very dry retired Marine officer who told me in complete monotone/no emotion: "The .223 is perfectly effective at killing 200 pound mammals out to 200 yards with one shot if the shooter knows where and how to place the bullet. Anyone will shoot the .223 more accurately than anything else because it has no recoil and is inexpensive to shoot. With a proper bullet shot placement is everything, the rest is fluff."
He also admits that he would never take it elk hunting (reminding me that he limits size to 200 pounds) and only takes broad side shots at 200 yards or less. He and his sons (one is now a Marine and works on V22s) have come have come home from multi-day deer hunts empty handed after seeing many deer because, "no targets presented an appropriate shot, so we didn't shoot anything."
He uses factory loads with, I think, noslers. he only shoots this one factory loaded round because, "why would i screw around with different loads and bullets? That's dumb." I asked him about reloading. He doesn't because, "I did the math on the equipment, the required space and my time. It didn't work out so I don't reload. If you tell me that reloading will improve my shot group or increase my chances at killing an animal, you are wrong."
Funny/dry humored guy who is the very definition of practical, doesn't hunt elk, stacks up coyotes and a few deer and likes time outside more than time screwing around with guns and loads.
I'm different but really appreciate his approach.