There was a handful of 6mm PPC's (and also .22 PPC's) made in the #1. I have not seen one in a long time, but ElNumeroUno has a .22 PPC for sale on his site, if you want to PM him.
The breech face is flat on the #1 - you may or may not need to fiddle with the extractor to get it to work.
Ruger's now building a K1V (stainless bull barrel) in the .223, and I'd wager it should shoot quite well.
