As noted your charges will need to be compressed. Take a look online and you'll find that there are Powder Swaging dies available that are intended to specifically compress a black powder charge prior to inserting the bullet.

BTW, stumbled on that looking for a press mounted push through swaging die to allow re-sizing .357 bullets to 9mm diameter. While I don't currently own or load a 9mm some forward thinking had me looking into using 38 caliber plated bullets for 9mm in a pinch and a carbide die to swage the diameter slightly would have been ideal for that task.