The .270 has a better ballistic coefficient than the .308.
The .270 will shoot farther and flatter with more energy than the .308 (in the same bullet weight) because it has a smaller cross sectional area.
True but I’m hoping for .357. .450 works fine also.
Rule .308 comes from Rule .303. There is no Rule .270.
The highest BC for a Sierra .277 bullet is .508. .308 diameter bullets top out at .800, but you would not shoot those in a .308 Winchester cartridge.
yes, but on https://ammoseek.com/this morning the cheapest .270 is 89.7¢ a round. The cheapest .308/7.62x51 is 60.0¢ a round.