I’m Luke warm on the .243 but the 80grain TTSX has warmed me to cartridge a little. A bullet in the lungs will kill anything, but I do prefer an exit wound to leave a heavier blood trail, especially down here where I hunt whitetails. Complete penetration has not always been my experience with .243’s
Fwiw, I bought one for my daughter a few years ago and it has killed about 20 deer, a dozen Javies, and a couple antelope between her, her friends, brother and cousins - most with the 80 grain TTSX. Come to think of it, I’m not sure why I’m still iffy on the caliber.
Here is a pic of a 150lb field dressed buck’s leg bone immediately below the shoulder blade. My daughter shot this past season with the ttsx. Shot was about 110 yards, it did pass completely through.