Well I haven't found any loaded 6mm ppc myself. Haven't seen but handfulls of very expensive brass either, but I haven't looked hard.
I just bought the varmit 6ppc from Mod1... I'm still waiting for my dies... As I reload, I plan on making brass from 7.62x39... if you don't reload the Grendal has ammo availble midway and a few others (check out the grendal site), but its a bit pricey.
As for the grendal, good luck getting anything but an upper from one of Alexander's distributers. I pursued this before I bought the 6ppc from mod1. Guys will custom make you a barrel but no one will stock and sell them enmass for fear of copy right infringment, and I haven't seen any offerd by Alexander or there distributers.
6.8 spc... seems like a nice Idea, but the grendal will out perform it ballistically, and seeing you can seat bullets out farther if your a hand loader and they still will work through the mag I'd rather have the 6.5 grendal.
But I bought a Grendal mag for my 6ppc am having some trouble, and I haven't even put one round of 6ppc in the magazine!
See this threadBut I'm a newbee as well... what could I know.