My 1880 Vintage Westley Richards has 12 bore dimensions and practically no forcing cones.
I do not quite follow what you are saying here. Nominal difference between 12ga chamber end & bore dia is about .070". Whether long or short this reduction in size is in the form of a cone, "unless" it is one of the very early guns with an abrupt step, which would be unusual as late as 1880 I think. If it is in fact a "Long Cone" rather than "No cone" it may well have been intended for use with brass shells to ease the wads into the standard bore size.
