Well, this one got opened up again (actually, it never closes) so here’s what I can put forth:
I’ve shot probably ten times as much .30/06 ammo over my career as I have .270. Just about all of the guns I test for the magazine are chambered for the ’06. That’s because it’s the most popular and useful cartridge around, and with the huge variety of ammo and bullets available, you’re bound to find something that works for any given rifle.
On the other hand, I’ve done far more hunting with the .270. I like the higher velocity and lighter recoil. Most shooters will do better with a .270 than with an ’06.
I have yet to see any real difference in killing power between the 130-, 140-, and 150-grain .270 loads. There are big differences, however, in bullet make and type.
The most useful bullet weight for the ’06 is either the 165 or the 180. It depends on what you’re hunting. The load that deserves more popularity is the 200-grain. Right now, I don’t know of any factory that loads it, but it turns the ’06 into a fearsome killer of large animals. I had one .30/06 that would give me 2,700 fps with that bullet, and it was hell on wheels.
For whatever reason, it’s not unusual to find a .270 that will shoot all three bullet weights into the same group at 100 yards. However, it’s extremely rare to find an ’06 that will print any two weights together.