Seems to me, steel, tungsten and bismuth are available in 2 3/4" and longer cases, in smaller shot sizes.
I think I would be inclined, for migratory birds, to use tungsten shot.
I have heard good things about Federal Black Cloud steel shot
however bismuth shot from Hevi-metal is about the same price, as black cloud steel, seems to me. The heavier pellet weight is a good thing.

https://www.rogerssportinggoods.com/hevi...waterfowl-loads