I believe that if it can be used on an autoloading shotgun, IE the 870 model fits the 1100 & the 11-87, (and it does) then no way they will let it in, because it is technically a 23 round magazine for an auto shotgun and the feds wont care about its possible applications with pumps. If they were going to allow it it would have to fit the pump shotie it was made for and nothing else. They make a ton of models but if the same is true for the other manufacturers then we wont see them here.
I'm NOT an expert, this is just how I understand the law as its written up in the guide. It's been a while since the last post on this, does anyone else know anything about their status?