I hunted with a Ruger No 1 .243 Win for a lot of years and it killed deer just like my .30-06 did except with a lot less recoil. There is a well known PH in Africa (whose name I can’t remember right now😳) who champions the .243 for Leopard. One of my early Centerfire rifles was a Remington 722 in .244 Remington and shot a boatload of deer and pigs with 90gr bullets. There is not a lock of difference in the two

Guns don't kill people, it's mostly the bullets