Back in the day when you could use spinning wing decoys I shot a 20 guage shooting 3" Kents... mostly size 3s w/ IC and Mod chokes in my O/U. That was mostly early season stuff.
I primarly shoot 3" 12 gauge... again Kent Fasteel in 3s and 2s for ducks. I've had good patterning in both IC and Mod tubes on my 12 autoloader.
Geese.... 10 gauge 3 1/2" BBB Rem Steel through Mod.
All the tungsten stuff is too rich for my blood and I haven't seen any significant difference in killing capacity when I've shot Bismuth. Looking at the density measurements on it, it's actually not a whole lot better than steel. I may have to try and reload some the the hevi-shoot.