Thank you all for your comments, Gentlemen.
Fernando, the brass section on the barrel mouth is only a sheet applied to the steel and, surprisingly, not fully around, but only covering the visual part of it; definitely a decoration purpose.
I see your point that the hook would be for a sling (talabarte) due to this gun's weight, although its shape is precisely that of a waist belt hook (gancho de cinturon).
You are right in that the ramrod (baqueta) is not the correct one; it is going to be a problem to get a wooden one with a brass or bone tip, but i will give it a try.
Marcus, i agree with buck shot being basicaly the ammunition for these things; even some times all kinds of junk pieces, as per circumstances. When i mentioned 'caliber' was only to give an idea of the bore diameter.
Thank you Mark for the naval approach
. It is possible, yes; but we can't discard the stage coach or armed guard possibilities, this one based on the waist/shoulder hook presence.
.