Gun cotton was an old form of explosive. But it can be very dangerous. It is possible to make it, but not practical to use for small arms. I reload.
Black powder is also easily made from scratch, but it is corrosive. And it is often an unstable compound. (precision issue)
Black powder gets around the issue of pressure containment by having all loads compressed, no void space in the barrel or in the brass cartridge if it is not a muzzle loader.
“Gun cotton was an old form of explosive. But it can be very dangerous.”
You are far more knowledgeable than I.
I have noticed many Ukrainian photographs and reports do appear to reference the huge “cotton” clouds that form following the bombing. But, maybe I just view the images that way.