I used to carry one of those derringers, although mine had shorter barrels. I carried a .45 long colt in the upper barrel, and a #4 .410 in the lower. The long colt hit the target sideways 9 times out of 10. It was a handful to shoot, but I really, really, would not want to be in front if it when it went off!
Wyattearp,
Remind me never to tick you off.