Here is some comparative info:
.460 BC .270 @ about 3200fps 130 gr Hornady superformance GMX factory ammo
yards | fps| energy | trajectory | come up MOA
1000 1853 991 -206.1 19.7
.59 BC .270 @ about 3090fps 140gr cutting edge bullets hypothetical handload
yards | fps| energy | trajectory | come up MOA
1000 2034 1287 -198 18.9
.6 BC 6.5 SAUM @ about 3250fps 140gr cutting edge bullets hypothetical handload
yards | fps| energy | trajectory | come up MOA
1000 2175 1470 -186.5 17.8
The 6.5 SAUM is better, and it has the advantage of being a short action (lighter weight), but I'm not sure it's worth the effort. Apparently the 270 has enough velocity to do the job at 1000 yards, no clue how flat those trajectories are (don't know what's considered good). The upside of the 270 is I already have it and there are lots of options out there.