The .500/.450 NE is a great cartridge, no doubt. Without the .450-component ban in the colonies, it would certainly be more commonly seen today, and with the plethora of inexpensive .458 bullets it would be a marvellous choice for all-round heavy game.
bonanza: I think you might find, though, that the .450 NE (Rigby, or 'straight' 3 1/4" cartridge) would have gained the front running between the wars. It allows a slimmer action, and hence a more elegant gun, or alternatively more steel in the breech for better weight between the hands, than the earlier black-powder conversion .500/.450. The larger powder capacity of the necked-down .500 case was no longer needed in the smokeless era, and in fact was not even of much value in lowering pressure in the post-cordite era.
Nevertheless, either cartridge makes a fine DG double-rifle chambering today.
-------------------- Marrakai
When the bull drops, the bullshit stops!
--------------------------------
www.marrakai-adventure.com.au