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.
When I was a kid 10-14 I made lots of gunpowder. It’s really very easy and not too unsafe in small quantities, outside. I did have a few accidents but nothing catastrophic. Amazing what our parents let us do back then. Eventually I even made gun cotton (a nitro explosive/propellant).
“Usually newbies attempting to make their own primers or gunpowder are a self-correcting problem, if you know what I mean.”
Gaza work accident?
The Japanese make truly spectacular fireworks including bombs and mortars having powder and fuse for re purposing
A battery and spark plug will set off black powder.
However, if fireworks are legal in your country, a LOT of improvised weapons are possible. And possible in relative safely. Including some stuff that an MRAP would think twice about. Of course, good ole gasoline and a glass bottle has been fine against armored vehicles for 100 years now.