Primers should not basically fall in with little or no resistance.
Didn't appear very accurate.
It's been a long time since i've used pyrodex, but with BP, shotgun rds are normally by volume. The payload volume and powder volume are equal, or close to it. I don't think that scoop was equal volume to the slug. If not, it would be rather anemic. If that slug is hollow, just a piece of felt cloth is not sufficient. The hollow base represents an air gap, which creates a dangerous situation. An over powder wad at a minimum, but even that may cave in too easily. A cushion wad would work, but you'd want the over powder wad, as they typically disintegrate, and might leave parts of it in the bore.
And acrylic felt, melting in the bore from the heat. I bet cleaning is fun.
Yes, I found myself thinking... "I might what to use an over powder wad and cotton wadding" as I watched it.
To be honest though, I can see the merit in the basic idea (even if I might be inclined to try a round ball instead). Basically load a shotshell the exact same way you'd load a smooth bore muzzle loader and pop it in the chamber.
I was also thinking, if not using a cylinder bore... one might want to check for fit at the muzzle of a choked barrel. Having both a Pardner Pump Protector with cylinder bore and the hunting model with a choke tube (modified) I'd want to be safe in both.
The hunting model with a rifled choke seems to present an interesting possibility too.
That said, I also have two Pardner single shots with modified choke. Strikes me as the best choice really. Easier to single load single shots that to side single load the pump guns.
I was thinking it might be a fair way to test and use home made black powder in all honesty, as well as an easy way to make a few slug rounds when needed or desired. Given the weight of slugs and round balls of appropriate size, high velocity wouldn't be needed to get the job done. I'm thinking 1000 to 1200 fps would be plenty, and easily in reach of the usual 2 to 3 dram black powder weights that were used back in the day.