The author of a book about hunting in India wrote 1900 that the more inexperienced the hunter is, and so larger the caliber used should be for shooting heavy DG. Back then, he recommend a DR caliber 8 or better, one caliber 4. As for the cartridge 577 Nitro Express, he was somewhat skeptical because of the new nitrocellulose powder.
To get back to the present day, anything more modern cartridge of caliber .416 upwards with a premium bullet is well-suited, certainly somewhat better than the cartridge 450-400 Nitro Express for elephants. I would therefore prefer the cartridge 450 Nitro Express for a DR.