Here in the US we have a 1/2 inch limit; but there are exceptions for "sporting purposes" whatever the hell that is... I suppose more to the point, since this is a fantasy after winning the lottery, then the modest fee of a $200 is hardly an issue to go over 50 Caliber for a proper (looking) Howdah cartridge.

A safety cocker/decocker like the K-gun system would be a modern touch but Id still want hammers. No one has mentioned an O/U and Id kinda like to see that at least as an option just because options are nice. Ive seen the S&W 500 X Frame with the short barrel (I think its 5 inches) and the BFRs they are HUGE and not that its an issue on an elephant; but they seem disproportional to me.

Now dont slam me for this but Ive kinda wondered about the 3 barrel shotguns (third barrel on top). In 20ga it wouldnt be Tooooo large??? they have a single trigger, which on a shotgun I dont like since it doesnt allow for barrel selection BUT on a Howdah meant to be fired fast at bad breath range might be a good option.