My latest .222 Rem had a used .22PPC Hart barrel on a rebuilt 40XBR action.. It did better than yours!
21.00 grains IMR 4198/Fed 205/Lapua M cases/52 grain Gentner FB (RIP)
Lothar Walther is not in the same as Shilen, Hart , Lilja, Krieger, Bartlein and ......
I have never shot a Lothar Walther...