Going out on a limb here...
Is it a 458SOCOM?
The .45 Blaser cartridge is one of the forgotten heroes.
It is (was) a German attempt to create a subsonic sniper cartridge.
It is said, development was initiated by the German Ministry of the Interior.
But finally, Germans decided velvet gloves are better than subsonic cartriges for dealing with criminals, and the concept was droped.
Blaser piced up the idea, and offered the supersonic version as a hunting castridge in its R93 straight pull rifle.
Worked great again, like a full house .45-70 Government, but was not a commercial success...... and was discontinued again.
Cases are still available from "shm Sueddeutsche Huelsenmanufaktur"
Sorry for hijacking the thread....