I can't help you with a double
But I hunt with a single barrel Austin & Halleck ( SP) and a TC New Englander
Both have choke tubes rated for steel shot
I run LM or Mod chokes

For ducks I run 1 1/8 oz of #2 Steel , a 2 3/4" steel shot wad , 100 Gr equ of 777 with a overshot wad to hold it all togeather

For geese I run 1 3/8 oz of Hevi #4 or #2 , 3" steel shot wad , 100 gr equ of 777 with a over shot wad to hold it all togeather

Both loads were OK'ed by the manufactures , but my be to hot for some muzzel loading shotguns or the shooter

YES it is a PITA to clean the wad smugges out of the barrels
But I kill ducks and geese with no problems


John