RE: killed elk with which cartridges?
Three with a .270 WBY Mag. One with a .300 WBY mag. One with a .338 Win Mag. One with a 6.5mm x .284. One with a .260 Rem. Two with a .284 Win. Two with a 7mm-08 Rem. One with a .308 Win.
I like the 7mm-08 in cover (up to 250 yards or so) and the .270 Wby Mag in open country. Both are fairly pleasant to shoot at the range...which means lots of practice, great accuracy...and no flinch.