empirevr:
As John the Greek says, not everyone agrees with 500grains and 400NitroExpress....

Here's a telling paragraph or two on the 8-bore which might interest you, penned well into the smokeless era by R.C.F. Maugham, inveterate big game hunter, and His Majesty's Consul-General at Beira, Portugese East Africa, after the turn of the previous century;

"....no hunter in his right senses should place his blind trust in such a weapon as even the .450 cordite rifle to extricate him from the thousand and one dangers by which he is liable from day to day to be confronted in Africa. I therefore unhesitatingly advocate, in addition to the most perfected type of modern high-velocity weapon which we are ever likely to see, the inclusion of a sound, heavy rifle intended for use at close range, the shock of whose bullet, even if it should not instantly kill, will assuredly be sufficiently great to disable or turn a charging beast."

His recommendation?
"..a heavy eight-bore, which I look upon as the ideal weapon par excellance for this purpose".

And "For those who do not have the strength to use a heavy 8-bore"?
"I would suggest the adoption of a 10 or at least of a 12-bore paradox throwing a 1 3/4 ounce bullet, driven by a charge of 5 drams of black powder. This, in capable hands, should be sufficiently powerful to produce the desired stopping effect".

Holland & Holland apparently agreed, listing their 10-bore paradox "for rhinoceros, bison, and other kinds of large game" in the 1904 catalogue, and the 10-bore nitro paradox "for elephant, rhinoceros, bison, and other kinds of large game" in the 1910-12 catalogue. The 8-bore paradox was listed simply as an "Elephant Gun" in both catalogues.

There is a surprising degree of ignorance about the capability of bore-guns and paradox guns amongst those who have never used them. Sadly, with the cost of a single elephant or rhino in today's Africa, very few modern hunters are ever likely to discover those capabilities for themselves.