rockingbbar: "Those old Kentucky rifle play guns that used to shoot cork round balls used to make decent shotguns when loaded with a couple of fire crackers and a wad of BB's in a bit of rolled up paper towel.."

Yessir! I had one of those play Kentucky rifles.
It had a place where you could put a cap, like from a cap gun. Then you put a cork ball down the barrel.
The power of the cap would shoot the ball about 40 feet.

I got 5 black cat firecrackers and poured the powder down the barrel. It was a very fine, silvery powder, almost like dust.
I found a marble that fit the bore real well, it was about a .45 caliber bore. Didn't use a patch didn't know about that.
I knew that the thing was liable to blow up. I wedged the rifle in a bush. I tied a 30 foot string to the trigger and got back about 28 feet.
The rifle was aimed at the neighbor's concrete block foundation.
I pulled the trigger and it fired! Big cloud of smoke, big big bang.
I went over to the neighbor's house and there was a one inch hole in a concrete block.

The gun didn't blow up, nor even swell up much.