I would agree with Larry O's comments about the other rounds.
I will also say that the 270 AI is a fine round. It is to the 270 Wby what the 280 AI is to the 7mm Rem Mag.
IF you want a long range number get some of the Wildcat Bullets .277" 169.5 gr Rebated Boattail ULDs. These bullets have a B.C. in the .750 range!!!
Another great AI round and perhaps my favorite is the 6.5-06 AI. While it is a little more fuss to load then the others that use factory ammo, it really is not that big of a deal.
All you need to do is take 25-06 brass and chamfer the inside of the case mouth well and seat a boat tail 6.5mm bullet in the 25-06 case.
You won't even be able to tell the mouth is 0.007" undersized with the boattail bullet. Then fire and you have it, a 6.5-06 AI.
If your set on the 270 caliber and are nervous about bullet selection, again contact Wildcat Bullets and ask about the new bullet weights being designed for my 270 AM round.
Along with the High B.C. ULD bullet, there will also be a bonded Core FBHP and bullet weights in the 160, 170 and 180 gr class. These may be a little heavy in the standard 270 AI case but they will offer performance above anything offered in this round to date.
You may be well seved to get a 1-8" barrel though if you want to shoot them.
Here is the e-mail address for Wildcat bullets: