Regarding fast reloading of muzzleloaders with multiple barrels (pepperbox, over/under derringers etc.)
The goal is to be able to reload the gun faster than you can reload a modern cartridge revolver using a speedloader. Since you don’t need to manipulate the cylinder and extract spent cartridges, it’s not an unrealistic goal.
Maybe a combination of these designs will work?
https://youtu.be/Yf9mM15TRCY https://youtu.be/56ODcH2C_Xw
attaching a magnet that stick to the muzzle holding it in place while ramming everything down with a ”multi-ramrod” is my spontaneous thought.