You know as much as I am a 270 fan the arguments abojt higher bc bullets for a given caliber changing the game applies to literally every caliber….and with bigger bores and bigger cases still the long range potential is always gonna be greater with sufficient twist.
At some point we'll just have the highest bc bullets tangibly possible in every bore diameter haha, at which point .007 of an inch won't matter much (.277 to .284 for example).
The highest bc .22 pills come close to the highest 6mm ones but not quite. Same for 6 to 6.5. Then same for 6.5 to 7. Then for 7 to .30 cal (and yes it's true…not aware of any 7mm bullets quite up there with the 250 ATIP.
Keeps going that way. There are bore diameters along the way hamstrung by slow twists historically (25, 27, 35…I have rifles in all of those calibers and no 6.5 or 7 haha) but that's all there is to that.
So it eventually just become a question of how big and high bc a bullet you feel you need and how big a case would be required to drive it to the velocity where that bc would still be advantageous (there's lots of .338 bullets that have way higher bcs than any 7mm but if youre starting out with 300-600 fps disadvantage out of a much heavier rifle that still generates more recoil and is much more pricey to practice with you gotta factor that in too).
This is why 7mm and 30 cal mags are unquestionably the kings of long range big game hunting if we're going off popularity. They're big enough to have some very high bc pills that can be driven very fast in cases that still fit "normal" mass produced type actions and while snappy can be controlled my most experienced shooters in rifles that don't seem like artillery pieces to carry in the field. The sweet spot.
Also thinking of military history…now we live in the age of intermediate cartridges but thinking back to ww1 and ww2 era battle rifles…various countries did experiment with bigger and smaller bore diameters but overwhelmingly, proven through real world observation of efficacy, they all seem to have more or less concluded that a sensible field rifle/battle rifle cartridge capable of long range engagements and close ones as well was going to be somewhere between 6.5mm/.26 cal and 8mm/.32 cal.
Smaller had issues (6mm lee navy anyone?)…and there's a reason the 45-70 became obsolete as a military weapon - I recall reading about some battles during the American Spanish war that saw Americans with 45-70s getting their butts handed to them by Spaniards with 7x57 mausers - couldn't effectively shoot back at the distances they were being engaged at - that 11mm Mauser or 43 mauser sucks ballistically as well)
6.5 50 arisaka
6.5x55 Swede
6.5 52 carcano
7x57
280 Ross (an ahead of it's time cartridge in an ill thought out rifle that was reportedly ditched by Canadian troops in ww1 as soon as they could get their hands on an Enfield .303)
7.62x54 r
7.5x55 Swiss
The French and argentine cartridges I can't remember the specific numbers for
.30-06
7.62x51/.308
.303 British (.311")
7.7 Jap
8mm lebel
8x57 mauser
There's no doubt many others, but pretty much every single battle rifle or field rifle cartridge before the age of intermediates and "assault rifles" was within the .26-.32 caliber window. It just makes sense, the right amount of everything.
Of course there were many other calibers and rifles used in war but I'm talking issued en masse to troops.
This rabbit trail to point out its becomes largely arbitrary after a certain point to try claiming there's anything special about any given bore diameter as far as magic bc potential. The bigger the bore the higher bc potential, but twist rate and case capacity determine if that matters or is practical. I love my 270. The 6.5 and 7 sandwich it and i Honestly see no need to try turning the 27 bore into yet another version of the same things it would be competing with.