IMO you just wont get that much out of an improved 270 win to make it worth the expense of a new barrel.
If you are just going to ream a barrel you already have then not such a big deal.

Have you tried RL17 yet. You could probably get another 100 fps with it.
The new power pro powders should get you +150 fps. That might work in a 270 AI pretty well.

Actually if it were me in a long action I would be looking at a 280 AI to shoot the 162 gr amax. A great bullet and its cheap.
Has a BC of something like .625.

I shot a 250#+ hog at 300 yards with the 162 gr amax in a 7mm-08 and it blew through him like a freight train.
You could probably get about 2950-3000 fps out of a 162 amax in a 280 AI with a 24-26" barrel.