I made my first batch when I was about 12
using my mothers marble mortar
ITS NOT RECOMENDED TO DO IT THAT WAY , but I was just a child
last time I made any bp I used a ball mill to crush all ingredients separately,
when all 3 are just a very fine powder you mix them together in the ball mill and add a suitable amount of water. not to much , but absolutely not to little either.
better with a little to much water, should be a thick slurry .
then you let the ball mill tumble for another few days , the longer the better quality on the powder.
4-7 days I let it go
then you take the powder (slurry) out and lets it dry until its in the same consistency as ceramic clay.
then you push it through a fine mesh net, mesh size depend on wished granulation size .
the result you got then looks like black spagetti
let it dry outside in the sun, crush it between your hands or between 2 pieces of plywood .
if you want to be really serious you can make a hand cranked rolling mill with rubber rollers that have an adjustable space between them
when thats done its time to let it pass trough a sieve,
or preferable different sieves with different mesh size to get different granulations
if its done this way it will be the same quality as commercial black poder
the only difference will be the color , this will be more grey then black .
commercial powder are polished and graphite coated, thats what gives it the black color and it prevent dust from the powder .
homemade bp gives an much more relieable ignition when used as priming powder in flintlock guns .
milling balls must be lead balls
whatever you do , dont use steel balls