Look at the ballistics of the Barnes bullets. In 243, you are still well over 1000FP of energy at 300 yards
i am going to have to say the 30.06 with decent glass. very versatile round, and ammo is readily available.
That .243 should work fine, but out to 270yds on a big pig, I don't have any hand's on advice. 30-06 all day long. If you've got the .308, I would just stock up on the ammo for it. They usually run the same price as 30-06 or 243's as well.
I'd say just about every gun you already own/listed could fit the bill very well with a premium bullet like a nosler partition or a tsx. the 308 would be the real winner, plenty of power/range/accuracy and availability of ammo. I love my model 7 due to the size and ease of carrying, and with a good load/bullet would be able to do anything you described with a smaller/lighter gun. those would be my top 2 choices, of what you listed. if you didn't own any guns, I'd still pick a carbine length 308.
I went with 30.06. That said every store i have been in in the past two months looking for ammo always has .243 and .270 on the shelves when the rest is gone.
