Flat-shooting, BTW, is a misnomer.
Look at this chart:
http://www.remington.com/products/a..._results.aspx?data=PRC270WB*PRC308WA*PRC3006B
I took 3 good-quality Remington hunting loads, one each for .270, .308, .30-06: 140 gr., 150 gr. and 168 gr., as appropriate for the rounds, all Premier Core-Lokt Ultra Bonded bullets. Take a look.
Sighted in at 200 yards with the scope 1.5" over the bore, here's the drop in iches that you get at 250, 300, 400 and 500 yards.
.270: -3.0 -7.6 -22.5 -46.4
.308: -3.4 -8.6 -25.5 -53.1
.30-06:-3.3 -8.5 -25.1 -51.7
Yes, a drop of just
under 2 feet at 400 yards is "flatter" than a drop of just
over 2 feet! But either way, you'd better know your range and compensate for the drop, if you really think you'll be shooting that far. At 400 yards, all three rounds drop
about 2 feet, no matter how you slice it.
Particularly with all the new scopes that come with reticles that show bullet drop, I really think "flat-shooting" is WAY overrated.
The difference between the drop of a .270 and a .30-06 at 400 yards is about 0.7 MOA, in other words less than or equal to a good hunting rifle's group size from a machine rest, and several times less than a good hunting rifle's practical accuracy in the field.
The various similar spitzer hunting bullet trajectories are so similar at ethical ranges that they should be chosen by other criteria instead: recoil, gun size/weight, desired barrel length, price/accuracy of rounds, energy downrange, desired bullet weight, even bolt throw as mentioned above.
The really good reason to choose a .270 over a .30-06 would be that you want to shoot 130-140 grain bullets, not because it shoots an inch "flatter" at 300 yards.
Just MHO.