Can pyro-pros answer

What differentitates the bp that is put in a closed container that goes boom from the bp that will not go boom instead it is used for launching rockets, for a long time I tought bp is for explosives and firearm, do you not have to mill it or different ratios, or idk, I usually just mill mine (75,15,10) for 24h and use it for small petards

Thank you for any answers!