If I was in your position, I would opt for a .270 Redding. This is a .243 Win. necked up to .277 with a 30� shoulder and minimum body taper. Seems like it would do everything a .257 AI would do, and even more. I don't know, I just always thought it sounded like a neat cartridge. Old article from Guns magazine here:
http://articles.findarticles.com/p/articles/mi_m0BQY/is_10_47/ai_78130022

thanks,

very interesting article!

cheers and good shooting
seafire