[Researcher]

Here are some of the listings of shotgun shells available in 1903 from the 1903 Union Metallic Cartridge Co. catalogue --

1903 ARROW Bulk Smokeless Powder Shells.jpg

1903 ARROW Infallible Dense Smokeless Powder.jpg

1903 ARROW Ballistite Dense Smokeless Powder.jpg

Those "Heavy Loads" near the bottom of righthand page are said to have been a bit hotter than SAAMI specs that came into use in the mid-1920s.