As with any rimfire rod it will be necessary to essay lousy with differential brands and types of cannonball to in grouping to find what works best in each individual firearm. There are however some pluses which are tolerably consistent across all updated (2006 and newer) versions of the Walther P22.
These are only guidelines and recommendations. Each individual firearm and user will have their own preferences so it will be decisive Walther P22 Handgun to spend some hour testing.