Mark,
I realize I'm not breaking new ground here but think about the 7mm SAUM. It's said to have the capacity of the 280 AI. That's about 50 - 100fps more velocity. Few would consider that a magnum caliber (even if the name claims it). You would probably be hard pressed to detect a difference in recoil compared to the 280. You also have the advantage of the short action which might be nice with the 24" barrel.
I think others gave you good advice to choose the rifle you want then select from the calibers avaliable.
Your only other option is the 270. There is only 0.007" difference in the diameter of the two calibers. I doubt you could look at a bullet and tell which caliber it is without measuring. There is absolutely no difference in on-game performance between the two.
If you are dead set on what you want, then wait and go the custom route when the timing is more appropriate.
HogWild
