Is it possible that the Waldläufer was originally chambered for the obsolete .22 WRF (Winchester Rimfire) cartridge? That cartridge was developed in connection with the 1890 Winchester rifle and was a much more deadly hunting cartridge than the .22 lr (lfB).

The .22 WMR (Winchester Magnum Rimfire) is identical to the .22 WRF in all dimensions other than in length, and .22 WRF cartridges can safely be fired in a .22 WMR chamber.