On average I'm getting about 70-100 fps more out of my 270WSM than with the standard 270 from 24" barrels.
I got a bunch of Nosler factory 325 WSM 200gr AccuBond ammo for a give-away price and have been using it. I can't beat it by hand loading so far, and it gives right at the factory claimed 2,950 fps with good groups...around 1" out of the Kimber.