About the video of reloading shotgun shells. A person could do this but why? It is so much more convenient to have a pocket full of shells that can be dropped into the chamber in seconds. If you only had one hull to use after shtf well okay go for it, but I would rather reload 50 of them at home. Anyway it so much easier to do it properly at home with a few simple tools and have reliable ammo to use in seconds.
Plus there are problems with the concept. A plastic shotgun shell is more elastic then a brass case. It will expand in the chamber then contract. A brass case will not spring back as much as the plastic hull. Getting the fired 45-70 case back into the chamber may present a problem. Consistent crimping on the bullet helps with accuracy. With an unsized fired case the bullet will drop into the case or it may fall out. Now you have a powder horn, loose primers and bullets. it defeats the reason to have a modern gun.