The biggest pre WWII caliber in a M-S was the 10.75x68, I owned one back in the 1970s and sold it because I could find no ammo source here in the USA. Have seen two more in the US since then. Meanwhile, they seem to be out there in Europe and Australia, per online sources.

The .458 Mag version of the Magnum Model Mannlicher-Schoenauer was made 1959-1968. No quantities available, however, I do remember a time maybe 10 years ago when the .458s and .264s were real drags on the market. Now a fellow Mannlicher collector has scored the highest price I have ever seen for any M-S in the current online auction. I will be hunting with him in June.