FYI just running the numbers on a 7mm 140 accubond vs a .277 140gr accubond, the numbers favor the .277 if both use a velocity of 3150. If we go to 3186 for the 277 and 3200 for the 7 the numbers still favor the 277with 1814fps and 1023fpe at 820yrds. The 7 @ 820 is 1798fps and 1005fpe. So why not get the most with a 140gr bullet. (all numbers are using Nosler numbers in Hanloads.com ballistic calculator) FYI even if you run the 7mm at noslers max it still comes up 1810fps and 1018fpe.
140gr .277 BC .496 max & 3186 max fps
140gr .844 BC .485 max & 3218 max fps
per Nosler "minimum velocities for reliable expansion 1800fps"
ok - sounds like you're pretty well married to the 270. I'm not at a computer with ballistic software, but try running some numbers for the 7mm 160grain AB (BC .512) and the 7mm Berger 168grain VLD (BC .617). Both of them can be pushed to 3000+ out of a WSM