I'm placing this here as a public service announcement in order to try and kill or offset a very dangerous urban legend I heard today for the first time.
Attended a gun show today where a somewhat scraggly-bearded man, all white hair, medium height, 50-ish approached me and told me how much he liked my cannon-shooting videos. He then asked if I made or bought my blackpowder. I told him I buy it. Then he said I ought to try making my own blackpowder but to SUBSTITUTE POTASSIUM CHLORATE for potassium nitrate in the formula, because it would "make a more powerful propellant". Warning from me: NEVER, EVER DO THAT!
Why? Potassium chlorate is a powerful oxidizer, and was often used in percussion caps and primers because when mixed with a fuel such as sulfur it makes a shock and friction and pressure-sensitive explosive. If you went through the steps used in making blackpowder, such as grinding etc. and used potassium chlorate instead, you would have a powerful, likely lethal explosion during the process, Even grinding a teaspoon of such a mixture would probably cost you at least one hand, one or both eyes, and probably most of your hearing, if a fragment of the mixing vessel didn't kill you outright. AGAIN, NEVER, EVER DO THIS!
I have no idea how widespread this rumor is, or how many people are going around spreading it, but please help kill this before it kills and/or maims someone or some number of people.