This is something I've wondered about as well, and I've tried to keep in mind when looking at old 'rifles'. To my recollection, all of the octogon-to-round barrels have been smooth bored. I'll go out on a limb and say that I think that probably most of the full octogon barrels were originally rifled, but many were shot out and reamed out, then used for shot for small game and pigeons. Remember all those passenger pigeons that were wiped out by the mid-19th century? That's my theory anyway, for what it's worth.
A lot of passenger pigeons were knocked off their perches at night with sticks, in fact most of them were killed at night.
The book "1491" points out that the masses of passenger pigeons were not known in early Colonial America, assuming the author is correct.
The rifle/smooth rifle thing is not resolvable to the point of knowing which were rifled and which not.
There are rifled 1/2 oct rifles too. We KNOW that some were built as smooth rifles.
There are surviving smoothrifles that are almost 100% certain unmodified in the bore.
We just do not know the percentages. Numbers of double barreled rifles are one smooth and on rifled.
But for use with shot they are inferior to a fowler or a musket due to stock design and bore size, both of these were far less expensive than a rifle stocked gun.
Dan