I have loaded plastic cases, plastic wads with black. Works fine once but don't expect many reloads the biggest problem is volume. You can end up using a wad designed for 1.5 oz shot and barely having room for an oz of shot. About 100 years ago there was a wad called a "LAG Unwad" It was simply a cup with an insert in the cup that crushed to compensate for volume. Ideal for black and 2 inch shells but I have not seen any for years.
bill
Bill, I THINK I have some of the LAGE Uniwads. I moved a year ago and haven't unpacked most of my reloading stuff(gunroom under construction) but I believe I have a couple of boxes of them. They were in a large box full of felt and paper wads that I bought at an estates sale. I didn't have any use for them but haven't thrown them away (yet).
To other questions.
I load all of my blackpowder loads in the green Remington Gun Club hulls. That is my way of identifying them. If they are in my gunroom and loaded, they are BP.
I use only felt and fiber wads. I have never weighed the BP for a BP shotshell. Volume for volume with whatever wad column gives me a proper crimp. Generally I load 1 oz of shot.