No
I am still looking for a Gras case with the rim thickness and diameter of the 8x50R Lebel case. thats what I learned by the pic's here.
remember that no original cartridge is known in the cartridge collector community till now.
the cartridge must have the exact OAL of the Lebel too!have said I measured .439 on the Vickers cartridge above the case mouth but in my experience with such measurements the real bullet diameter in the case will be allways a lttle bit above.
imho, a 458 cal. 350 grains softpoint reduced to the maximum diameter the barrel and the chamber will accept and loaded up to 600 -650 m/sec must be safe. that brings the load close to the 10,75x68 maybe not a real elephant cartridge but enough for australian water buffalo.