I know bullets are lead shot, any gun took steel shot?
US Federal Law now mandates the use of
steel shot for hunting any type waterfowl.
And like Mart said, bout anything they could drop down the barrel.
This was especially true in the late 18th and the 19th century when they were using 2 gage, 4 gage and 6 gage shotguns for shooting ducks, geese and Passenger Pigeons ..... to send to "market" in the big cities.
During migration periods they would ship those birds "by the barrel full" to the big hotels, etc.
The skies were
literally black for days when the Passenger Pigeons were migrating south for the winter. But they shot all of them but 1 .... and it died of old age while in captivity..