Has anyone tried this?

[JABN]

I stuffed through the barrel a plastic bag then threw down a small rock. This works really well since the rock goes really fast and its really cheap since rock don't are free and you can recycle the bag

[jrrdw]

Now find a cup that fits your barrel and fill it full of pebbles, it's now a shot shell.

Welcome to Spudfiles.

[saefroch]

Usually called wadding I do it all the time. So long as the friction created by the wadding (yes, I use bits of plastic bags too because they're retrievable) isn't too great, you can get a significant power improvement.

Welcome to spudfiles!

[Gun Freak]

It's like a the caveman inventing the wheel lol.
I shoot rocks too, they're fun... Welcome son

[Oppertech]

Rocks are always fun. If you have a .5" barrel, you can wrap pebbles in paper towel and it will feel like a musket. Just don't bother the neighbors, have fun, and keep safe!

[motorfixer1]

Crushed up spark plug porcelain also works quite well, even out of a wrist rocket. Something about its effects on tempered auto glass, not to incite some illegal mischief!