It's a smooth bore or it's a rifle it can't be both
actually it can be both . there were designs that had a barrel that was smooth at the muzzle but rifled at the breech .
A gun barrel having a rifled-bore section at the breech end thereof and a smooth-bore section at the muzzle end thereof, the sections having a gas tight connection therebetween, the rifled-bore section comprising a first generally tubular body having a longitudinal bore and at least one spiral groove formed in the wall of the bore to a depth of a predetermined dimension, the rifled-bore section having a length corresponding substantially to the peak pressure point for the gun barrel, the smooth-bore section comprising a second generally tubular body having a longitudinal bore coaxial with the longitudinal bore of the rifled-bore section, and the longitudinal bore of the smooth-bore section having a diameter greater than the diameter of the bore of the rifled-bore section and less than the diameter of the spiral rifling groove.
there are others IE over and under which had a smooth bore on the bottom and rifle on the top .
normally however a smooth rifle is a term used for a smooth bore that was built for the purpose of shooting a round ball , l and shot as an added bonus .
The difference between a smooth rifle and a fowler is that a fowler had a lighter barrel and desined to shoot shot yet capable of shooting RB.
a smooth rifle will also most times have some kind of rear sight . many trade guns were built with a rear sight . its a myth that smoothbores do not have rear sights.
this hold true for fowlers which most times do not have a rear sight
Here is a picture of an original SXS smooth rifle that I own .
What makes it a smooth rifle ?
The barrels are 42 inches long an near a ¼ inch thick at the muzzle and the center rib is near 3/4 of an inch wide . The stock is double wedge pins to hold the heavy charges .
it also has a n area wher a rear rifle sight was once attached
Now its true one could shoot shot from this as it’s a smooth bore BUT its to heavy and long for wing shooting which most SXS were designed for