I have a Browning A-Bolt 30.06, which I am planning on putting a new 24" barrel on. I was thinking of having it chambered in 30.06AI, but thought I'd throw it out here to see what other calibre's you think might be interesting options to look at.
This rifle will be used for everything from antelope to elk, moose and bear.
I am still debating about rechambering my Pre-64 M70 from 30-06 to 240 Weatherby. More as an Antelope/ play gun but not many people would have that caliber. Being "one off" is somthing that really turns my wheels. That cartridge wouldn't really be good for bears though,but I have seen people use a 243 caliber on Elk.
I don't know if there is ballisticly----someone here should know---but my 338 Win Mag A-bolt is a 26". I was just seeing if you had a reason for the shorter length.
I would assume that with a longer barrel your velocity would be higher, sort of like pistol versus rifle, but then again I don't know for sure.
In a 30-06, there is no reason to step up to a 26" barrel. Mine has an 18" barrel. I don't think I can use it if there is a burning ban, but it still works fine. Don't try to get crazy with an '06 and lose your portability. The gain of 2" barrel in a 30-06 will not be noticed in any performance measure except marginal differences on a chrono read-out.
I have a 3006AI and I enjoy loading for it, but only expect about 100 fps gain over the standard 3006. You don't gain much case capacity.
I wouldn't be afraid to tackle any of the critters you mentioned with that round. You can still shoot factory ammo in the AI if you have to in a pinch.
Other rounds to consider would be the 280AI or even the 338-06 AI or regular form.
The critters have to win every time, I only have to win once.