Doug - look closely as Casper indicates, but if they are straight rifled all the way, they'll still shoot better with shot and round ball than a totally smooth bore, however the rifling might pick up some lead now and then. The wads won't spin to open shot loads, and the ball will be prevented from spinning and taking off like a curve ball as well, thus better accuracy potential.

I have a straight rifled SXS Husky that is smooth choked modified left barrel and straight rifled 13 bore on the right. It shoots beautiful cylinder patterns with the right and of course, very tightly with the left.
The right shoots into about 2 1/2" on average at 30yards with black powder and round balls.

These straight rifled (Husky's)were developed by Husqvarna to beat the 'rifles only' law for moose law in Sweden back at the turn of the century. That they would also shootshot well for birds, was the intent. Mine was built in '98 or '99.