The guy who made the FGC-9 was harvesting nitrocellulose from ping pong balls to make smokeless powder, any method to get smokeless powder (which would be needed for any kind of auto-loading weapon) is pretty involved simply due to the chemistry required.
There's a thread in self-sufficiency on the topic.
Exactly, its the reason why in areas where ammunition can be sourced, you do see improvised firearms like the Luty in use (not THAT much though, as if you can source ammo illicitly you can probably also source the gun to go with it), however in areas where ammunition and its components are highly restricted you typically see cruder weapons that utilize black powder (like the gun used to assassinate Shinzo Abe).
Luty made .38 special ammunition using 8mm blank rounds as a base and shower curtain rods to fill out the rest of the casing, however I cannot for the life of me find the article which he made detailing their production (used to be on archive.org).