.22-250 rem., .220 swift if you handload

.243 win, or 6mm rem.

These are the only 4 I'd consider. I think I lean towards the .22-250 since I'm not much of a handloader, down the road if I take it up I plan to get a .220 swift, the .22-250 is so much more popular I think, just look at whats available for it in ammo.

Same with the .243, way more ammo available, though again I think the 6mm is a better round, as is the .220swift over the .22-250, considering either though.