I picked up a 14" barrel for my 12 gauge 870 from Dlask Arms for $300. I ordered it with a brass bead instead of a blade front sight,
and that along with the 14" length lets me pull it out of the rear quad box in hunting season and harvest grouse. If you get a shotgun
with a tactical blade sight, you won't be using it for anything that resembles hunting, it'll cover and hide the grouse. The other good
thing about the brass bead sight is that it doesn't snag on things when you pull it out. I also considered the 12.5" barrel but the sighting
plane was too short to make it accurate for hunting, so I went with the 14". I have the seatbox with the actual seat, and it fits just fine.