Id Unknown 1

Hi guys,
Going through my unknown bin and would very much appreciate some help to id this cartridge.
Bullet dia: 9.80mm -.386"
Neck dia: 10.25mm -.403"
Base dia: 10.70mm -.421"
Rim dia: 12.28mm -.483"
Primer dia: 6.45mm -.254"
Case L: 27.35mm -1.077"
Total L: 40.82mm -1.607"
Weight: 21.62g -334gr
Cattle killer?

In my opinion this cartridge is a non existent case type made from a cut-down 8.15 x 46 R.

Fede, thanks for the reply,
i have about 12 cartridges i will put on the forum to id, most of wich i also think are ‘modefied’.
They came included to a large batch i bought from a german collector.

My ‘guess’ of being it a cattle killer cartridge is the heavy weight.