This in an excerpt from the Norwegian gun magazine "Våpenjournalen" number 3 1998, written by the late Svein Sollie. I got the article and the English translation from a Norwegian shooter and Husqvarna expert:
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A Cape Gun for the Commons:

HUSQVARNA MODEL 17

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Just as the Model 20, the cape gun Model 17 was produced over a very long period of time. There were 3 different versions of it, the calibres being the difference between them. All
could be delivered with shotgun barrel in caliber 16 or 20, and you could choose between an ordinary smooth shotgun barrel with full choke or a straight rifled shotgun barrel with no choke. The argument for straight rifling seems rather vague; the original idea was that the straight rifles would keep the fouling in the rifling to make loading easier, but this makes little sense in a breech loader?

Some people thought that the straight rifles gave the shotgun magic properties, especially when loaded with a ball. Anyway, such barrels make a pretty normal pattern comparable with a cylinder bore when loaded with shot, and since the dimensions suit the ball diameter a
bit better than the smoothbore in same calibre, they normally shoot better than a smoothbore when loaded with a ball.
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