Fyi, one of the "burial objects" found with Spirit Lake Man (circa 12-14,000BC) LOOKS very much like a powder horn, complete with wood stopper & the remains of a strap. - It contains "some kind of unidentified dust", according to the chief docent of The Museum of the American Indian in DC.
I suspect that ancient man made containers from animal horn (that look like powder horns) as early as man had the means to make such containers.
When gunpowder was invented, I suspect that using horn containers for gunpowder quickly followed because those containers were "convenient".
MERRY CHRISTMAS, satx