High BC quarter bores are mostly a custom barrel game since factory twist is generally 1 in 10. Like the .277 options, there just isn’t much support with bullet choices because of slower twist rates. Notice all the bore sizes with lots of high BC bullets all come twisted fast from the factory. If you stay with calibers like .224, 6mm, 6.5mm, 7mm, and .308, you’ll have more options.
I’m a fan of .257 for no other reason than it’s different. I have a .257 Roberts and I just use 115gr Partitions since it’s just a hunting rifle. Been thinking a long time about building a 25 Souper with an 8 twist.