I usually don't comment on posts and living in PA, I have no moose experience. But if I was going moose hunting, the more practical question to me is...
When/if a grizzly wants you to share your moose with him, bickering about what caliber vs a moose seems moot.
I'd pick a caliber that would handle a charging grizzly, before I'd worry about the moose. (I've also heard that a charging moose will fill your pants, too!)
Either animal, my life may weigh in the balance of my caliber choice, and it won't be a 6.5 Creedmoor.
So, what caliber would I choose? My only experience with a big caliber is with a friend's 300 Weatherby Magnum (what a beast of a caliber!). I'd start by looking at that and going upwards. (I'd also have a holstered 44 Magnum with me, as well.)
Side note, I have another friend that uses his 300 Weatherby Magnum for whitetail deer. REALLY?? (I'm always on his butt about that...leave the butchering to the butcher, not to the caliber, I keep telling him...lol.)
He shot a nice 8 point this year and within days he went to his chiropractor AND the first thing he was asked, "You've been shooting that 300 W. M. again, right?"
One shot, one visit...serves him right, I keep telling him! We both laugh, he's a good bud.