The OP left a few things for assumptions, such as sporter, varmint, or heavyweight rifle.
For a new-ish LR shooter I tend to default to the 308 for the commercial availability of match grade ammo, decent ballistics, and modest recoil. Nowadays the 6.5 Creedmoor is in that camp too.
300 WinMag also has good LR ammo available commercially, and if you want one, and are up to shooting it well, seems like this whole discussion is fairly moot. The factory seconds may not hold up too well in the accuracy department out at say 600+, but who knows maybe they will.
If you want a sporterweight that is kinda like your 30-06, you may simply need to get a scope with turrets, and a LRF, and get to practicing.
I think most of us get into LR with what we have, then our needs/wants tend to evolve. It's the normal course of things. A lot of enjoyment and learning along the way.
