My Mossberg has a 28" barrel for hunting/trap/skeet, and an 18.5" barrel for home-defense. They do 18.5" on purpose, so there's no question the barrel is legal.
This one I'm chopping up is a rough old Stevens 16ga. single shot (50 bucks). It's for carrying on the ATV and the boat. Did the same thing to a Stevens .410 dbl barrel for a friend a few months ago.