One of the easiest endeavors in black powder reloading is the re-charging of brass shotgun shells.
Cartridge Cases - Hornady Manufacturing, Inc
Blackpowder Shotshell Loading Tips - Shooting Times
Shooting Black Powder Firearms, Reloading Black Powder Cartridges
MagTech 12ga 2-1/2 empty brass shotshells for reloading
Reloading new .450 (.455) black powder cartridges::Appstore for Android
Trench gun 12ga shotshells I made couple months ago : r/reloading
Shooting Granddad's Rifle: Reloading “Big Bore” Rimfires
What were shotgun shells made of in the 1800s? - Quora
Considerations for Handloading World War II-Vintage Rifle Am - Guns and Ammo
Black Powder Shot Shells
Remington™ Ulitmate Muzzleloader Brass Casings, X24153
Reloadable Brass Shotgun Hulls for Sale
Winchester Limited Edition WWII Ammo 12 Ga 2-3/4 M19 Brass Hull 00
410-44 cal. ???? - The Firing Line Forums
Throwback Thursday: Understanding Shotgun Shells 101 - The Shooter's Log