I thought I read this from a Husqvarna catalog on line, that the straight rifling was to circumvent a law passed back before the turn to 1900, that shotguns could not be used for moose - as was being done by the farmers. Thus, Husqvarna turned one or more barrels of the side by side 16 bores into straight rifling, which would still shoot shot reasonably well at close range, but also round balls from the "rifled" tube for moose, legally. I was told they also made twist rifle barrels, but I do not know if the larger sizes were made with twist rifling. Sizes of 20 bore, 16 bore and the 13 bore rifled tube I had were made. Also, the 12.2x47R which was their version of the .50/70 was also chambered up, usually in the left barrel/rear trigger.

The factory round ball loads always contained black powder as well as being in a brass case, so it was easily noted which was shot, which was round ball when both faced downwards in a belt. The shot load was in paper.

No - I didn't try smokeless in mine, although I was tempted just to use a load out of Lyman's handloading book for 16 bore 1oz. or 1 1/8oz.