Buying 270AI dies could be a deal killer. $110 extra from RCBS.
A .277" groove barrel and a 270AI reamer are priced on par.
257RI and 280RAI dies are ok.
One could make a seater die with the chamber reamer, and size with a Lee Collet 270 Win die. Pitch the brass when it needs a shoulder bump. That would be cheap enough.