Daryl,
Just out of curiosity, what powder charge did you use with those .684 WW balls?
If I get another chance to kill another moose I might do it with a 16 bore or a 12 bore. (both I have parts to make, but I have never had time to make them for myself. I am always working on someone else's gun, and have not made one for myself in 12 years now)
With my .600 balls I used 140 gr of 3F. The bull I killed with that rifle was about 70 yards away.