Watcha hunting? Wabbits? T-Rex?
Talked to a fella long ago, dumped all his deer w/a 6mm R600, 85 BTHP, up to 400 yds.
I'd buy a Ruger AR in 243, 19-20", plenty handy, though I know a local former LEO/trainer who used a 17" chopped 243 R700 BDL for a handy stand rifle.
Blast goes up and up, so 19-20 for me. More efficient IMHO would be a 6.5CM model, at 19-21" - Bigger bore, burn more powder INSIDE bbl.... = efficient