The .17 PPC is a necked down .22 PCC (or 6mm PPC if you like). You can also fireform .220 Russian cases to get a .17 PPC. Ultra light bullets, like 15 or 25 grs, can achieve speeds beyond 4500 fps. Well suitable powders, may be Reloader 15, H414 and the Finnish N550. With the fast, light en explosive bullets in 17 PPC, it performs very well on varmint game at short to medium long range. 

This text is based on information from “Cartridges of the World”, Hodgdon reloading manual, the cartridge designer and/or own resources.