For those who might be interested in antiqueguy's comment about smooth-bores in the UK, it's a matter of who can have them and who can't.
Basically, if you are over 18, of sound mind and health and have no criminal convictions of six months or over jail-time, then you can APPLY for a shotgun certificate with a good chance of success - given that you have good reason to possess it, like sporting activities. Using one as a game-getter would certainly give the birds more of a fighting chance, that's for sure, but somehow I can't see anybody except re-enactors being interested in a smoothbore Martini. Right now they have to have a proper Section 1 firearms certificate if they intend to discharge any Martini that has a rifled barrel, even if it's only with blanks, but a smoothbore could be held AND fired with a basic shotgun licence, in exactly the same way as members of the Sealed Knot - the English Civil War re-enactment society - have their matchlocks as shotguns.
I'll ask around on a couple of fora here in UK, and post the results- if any.
tac