Measuring by volume is pretty "iffy" at best, and isn't reliably repeatable for what we do. How fluffy is the charcoal, etc. Stoichiometric ratios for chemical reactions are an absolute must, so how much of what is always by weight. When too much or too little of a reactant is in a mixture, the reaction goes too slowly because the other reactant behaves as though it were a contaminant or impurity when it is in excess.
Back 60 years ago when I was in 8th grade, one of my buddies tried making black powder by measuring the ingredients by volume, using kitchen measuring spoons. I told him it was done by weight, but he wouldn't believe me. He said that wasn't how his mom measured ingredients to make cookies and cakes! His attempt at making black powder would just barely fizzle, and then go out. What he had was a pile of mostly potassium nitrate, with a little sulfur and some sprinkles of barbecue briquette charcoal in it. Barbecue briquette charcoal has a lot of sawdust and sand mixed in with it, along with some dextrin and Portland cement to make it all stick together.
Because my dad was a chemist, he had a one kilogram Ohaus balance that was accurate to a tenth of a gram. So, I mixed up maybe 10 grams, about 150 grains, of crude black powder meal to show my buddy how it is done, and how the powdered ingredients burn. I simply got some lumps of charcoal out of the back yard grill pit, probably lemon tree wood. In fifteen minutes I had made some fine dry serpentine powder, which made a pretty good mushroom cloud when it burned. Nothing like 150 grains of GOEX that I wouldn't dare get close enough to light with a match in my fingers, but a pretty good WHOOSH! That made a believer out of my buddy that chemists weigh ingredients, and that measuring spoons and cups are great for cookies and cakes in the kitchen.