Many years ago I took some 38 special cases and drilled and C-bored the heads to be press fit for a shotgun primer. I could pop them out with an ink pen and press new ones in with my fingers. I then set up a turret lathe to make some nylon hollow base bullets that were a slip fit into a sized case. They came out about .353 and weigh little to nothing.
They would shoot through a carboard box so I made targets by putting a box inside a box giving me 4 layers and that would stop the bullets in the center.
I taught my kids to shoot handguns in the garage with these things. Another added benifit was getting all the lead out of my guns.