You can load a 400grs , with a lower velocity , never equal the 450/400NE and the risk of poor penetration by shooting big game ! There are load data in the reloading manual of RWS .

The 10,75x68 is marginal for big game hunting , it's a good cartridge for heavy game at short to medium range .

I think its not fair against the good old 10,75.

there is a Deva PROOFED load for the 400 grains woodleigh bullet iirc with Vithavuori N 550 that can do this. N 550 is a wonder powder that was also able to make the old 9,3x72R legal on big game again in germany.