There's always someone who pushes the envelope. That was Langcaster's answer to John Dickson's three barrel gun. There are a total of two of the Dickson 3 barrel guns, and I have held one in my hands. It was much more lively in the hands than you would ever imagine (that surprised me). I think it would actually be a useful hunting gun, although I'd never buy one over a normal two barrel Dickson round action...the finest double gun ever made.
Dickson side lever 3 barrel gun
To my eye, there was no better maker of the two barrel gun than John Dickson, and his 1880 patent round action just stands apart from all the London sidelock guns.
This would be my Holy Grail gun. A skeleton action (woodside) round action, 16 bore Dickson. There just doesn't exist a more elegant shotgun, and in the hands, nothing balances or feels like a Dickson round action.