as the title, what materials or ingredients in modern gunpowder that if change to be expensive or rare to get, can ruin the evolution of advance gun or can turn modern gun obsolete or undesirable ?
i know generally gunpowder is made of sulfur, saltpeter, and charcoal (which i learn that it is abundant in earth some even from poop or guano so its unlikely happen unless earth get a massive catastrope/apocalypse). but modern gunpowder have some different chemical so far as i know (so i want to know the chance).
as i mention its about the materials or ingredients, so answer that say it prone to explode/kill the user or human never found the right measure or dosage because they are backward/brainwashed due to religion,tradition, pride,moralit,humanity, etc is out of this question.
but answer that include reason or some chain reaction like supply and demand or something that quickly depleting such ingredient for non gunpowder stuff that make the modern gunpowder ingredient expensive or rare is acceptable.
outright entire nation outlawing the ingredient just for the sake of banning modern gunpowder or gun like banning missile use because it kill to much people or too gruesome or can destroy the earth is out of this question.
natural massive catastrope to eradicate the chemical or modern gunpowder ingredients is out of this question.
gun was invented but not the type in ww1 to ww2 it stuck before this era, and they know gun was practical or massively advantageous in battle or to kill.
feel free to edit the tag to the apropriate one because i dont know which tag is apropriate for my question.