My eye opening experience with seasoning was with a Walther KKM.
I don’t recall what I was shooting prior, but I started shooting some TAC match and shot about 5, five shot groups back to back and watched the groups go from quarter/ish size with fliers to constant dime sized groups.
I will shoot a whole box at a time now, and if I change ammo manufacturers i won’t bother shooting for groups til I have at least 20 rounds through the barrel.
