.270 doesn't have as heavy bullets as the 30-06, or such a powder capacity.
Actually the 270 Win does have the powder capacity. It's the same case necked down. As far as heavier bullets, to get the same sectional density as the 160 grain .277 bullet you have to shoot a 220 grain .308 bullet. Why one would ever need a 220 grain bullet out of a 30-06 I have no idea.