If a gun can be homemade, cannot the shells also be homemade? Just curious.
Pack gunpowder into the back of a tube, optional washing between, then some projective from forms to bb’s. Aim, fire. That’s all it takes close range.
Usually the issue is that you typically need manufactured components like a primer. The primer is very difficult and dangerous to manufacture at home. Gunpowder is also not easily made at home, at least not safely. Usually newbies attempting to make their own primers or gunpowder are a self-correcting problem, if you know what I mean.
probably it was black powder charged—like the old time muskets—no shells needed