Oh boy. The PC's were based on the same brass as the 7.62x39 Russian (there is a .22 version... 5.45x39 or something like that). These have a rim smaller than the Mauser standard bolt face diameter... 8x57; 7x57; .30/'06; 6mm Remington (necked down 7x57 Mauser case), 7.62/51 (also called .308 winchester, slightly thicker rim, SAME diameter);... Remington, wanting to compete without alot of trouble, came out with the BR cases on the shortened .308 brass and a small rifle primer pocket (.30 UBR). Same bolt face DIAMETER as mauser. And about as good a rep as a benchrest/accuracy cartridge.
You could have the bolt face "bushed" to feed the smaller rim. This costs money. Alot. Or you can choose the BR cartridge which is so close to the PPC and no bolt face difference, no work. Then there is magazine work to feed the smaller diameter case. Costs money. Or use the BR which is same diameter as 6mm Remington... etc.
If he already has a 6 PPC barrel, have the chamber opened up... Save a bunch... LUCK