“A .410 would be better than a bullet, but I’d be concerned about its stopping power because it will have a wide pattern very soon and not much shot concentrated in that pattern.”
Tests of the Taurus Judge show (with Federal .410 handgun ammo) a 2.5 inch spread at 10 feet and penetration of 15 inches which is about the same as a 9 mm and is a very good number.The handgun ammo uses .36 ball, three or four of them depending on the length of the shell, 2.5 or 3 inch.
They are quite lethal in a defensive situation. As are the .410/.45 derringers, same patterns and penetration.
Seems like the Taurus Judge and the higher end Smith & Wesson 6-shot Governor are Derringer Revolvers...
S&W 6-shot with laser sight
http://www.youtube.com/watch?v=FikoFGBjra8