Looks like the ARC round is standardized and based off of the PPC. Biggest difference between the two appears to be neck length and consequently a pushed back shoulder on the PPC.
Having an AR heavy barrel in PPC I'm looking at converting ARC brass to PPC by just running the ARC brass through a full length PPC sizing die and trimming if necessary (maybe neck reaming too).
Any other concerns that should be addressed?
Alternatively, reaming the PPC chamber to ARC...(I already have dies and some brass for the PPC and a starting load that shows promise).