I picked up a BB some years ago. 12 gauge and a 14 inch barrel. It is, as already noted, a hoot to shoot. The most remarkable part of that is the short barrel. When the thing fires, it is all right THERE, in front of your nose.
Don't be surprised if the gun patterns tighter than you expect. I have only patterned mine with buckshot at 10 yards and the pattern was about the size of my wide open hand, maybe a bit larger.... about what you would expect at 10 yards from a cylinder choked gun.
Contrary to popular belief, the bell does not affect pattern size; its function is to make the thing easier to load on a platform that may be moving, like a stagecoach in the borderlands of Scotland or on the deck of a ship.
Pete