Anyone can now buy th emossberg 590 Shockwave pistol-gripped shotgun, in 20 or 12 guage, and it has just a 14’ barrel! NOT CLASS III! See here: https://www.gunbroker.com/item/774763821
If it has a BUTTSTOCK on it, it can’t be short than an overall length of 26”. Make sure you give accurate information here.
Wifey got one as her *carry gun* for bear insurance when delivering charter passengers [fishermen/hunters/firefighters] in her helicopter. They've had about 3 fatal bear incidents in our area over the last year or so, my 18-inch barreled Mossberg is a bit largish for her carry space, and her usual folding stock AK can go under her seat as well.
She's put around 400 rounds through it looking for the right load, NOT the same as what I use in the 18-inch tube gun, interestingly enough. Slugs are indeed part of the answer for bears, but only part of it and the definitive load has yet to be determined.
She's got a green laser mounted up top, too. They're not real effective below freezing, but until then, it'll do for her.