I use Norma cases and find them excellent.

Might want to try Norma ammo loaded with Woodleighs.

I was told that my rifle, which was made circa 1980, was probably regulated with Browning ammo and that Browning ammo was hotter than US 458wm ammo.

Regarding vintage, there is a member here who's tagline reads, "Never hunt with a cartridge younger than you are." I was born in 1961, the 458wm was brought out in either 1956 or 1958.

JPK