When I received my first gun in the late1960's my dad purchased some BB caps in the hope that I could use my gun like my BB gun and safely carry it around in the woods near our house (in the city). It turned out that they were much more powerful than he had anticipated, they could easily penetrate 1 or 2 pieces of 3/4 inch plywood, and were firecracker loud. That ended any hope of my using my new gun unsupervised.
Does anyone else have any experience with those BB caps, and does anyone know if any companies still produce them?