OCing long gun talk is technically a violation of rule 14, but since we're talking about legal 'shotgun' pistols and 'ar-15' style pistols, hopefully we'll avoid any deletions or closings.
rcawdor, do you happen to remember any names of the double barrel shotshell pistols you mentioned? I've been looking for something like that for a long time and never been able to find anything.
Also, I have a Bushmaster AR style pistol as well, but it only has a 7.25" barrel. A couple friends I've let shoot it in the past affectionately refer to it as "the fireball gun" on account of the beach ball sized fireball it makes. Never seen a holster for it, though.
Colt FMJ Model DD
Leinad .410/.45LC
There's about four more. The Leinad I have seen in person and if I recall correctly, they are "rifled" in a very superficial way for the .45.
Also note, SBRs, SBSs, AOW (only $5, not $200) are not uncommon in the state of WI. The laws cited above are preempted by NFA permission from the Feds to have them. So the blanket "it's illegal" is false if used in any sensible context where the state of WI isn't dictating laws for the entire planet.
Do your research before you buy.
Do your paperwork when you buy.
Do more research before making changes.
AOW covers the Serbu 12 gauge, which is NOT rifled. (The grip on the pump makes it an AOW.)