.284 based case in a CRF action requires someone with the time and know-how to make it feed properly. It's not some cosmically impossible task, but, certainly needs to be a topic of discussion with your smith if you lean that way.
If this isn’t an issue, and if you’re looking for some extra velocity, I’d be looking at the 6.5 RPM .
On the other hand a 6.5 - 280 AI has a similar velocity profile, with easier brass sourcing.
Either way it’s not too hard to extend the mag length a bit.
