"Karamoja" Bell killed many hundreds of elephants with the 6.5X54 Mannlicher and the .275 Rigby. The .275 Rigby is the Brit name for the 7X57 Mauser cartridge.
Taylor did not kill all his dangerous game animals with large caliber, heavy and slow bullets. One of Taylor's favorite dangerous calibers was the .375 H&H magnum: He killed over 1,000 elephants with his five rifles in that caliber. The .375 H&H is at the bottom of the big bore rifle scale and it does not fire slow heavy bullets.