I'd say the 22PPC is harder to find than the 6mmPPC. That's a good start on a 1V collection.

Now all you need is a 204 Ruger, 223 (both versions), 22-250 (non-prefix up through current), 220 Swift, 243, 6mm Rem, 26-06, 7mm Mag, 300 Mag, and probably a few others I've missed, not counting the ultra-rare non-prefix single copy ones like the 222 Rem and 308.