Otterbein has it correct.
Full case load of FFG black powder, moderately compressed, with a tight card wad on top. Tight, rolled crimp.
If you can get hold of military blanks and salvage the powder, you can make your own blanks. HOWEVER, it can get real dicey (dangerous) as military blank powder is extremely fast burning, and ANY sort of projectile loaded by mistake is guaranteed to blow up your gun. Don't even think about trying make a semiautomatic cycle using blanks. Even the military blank firing devices that are designed for this will occasionally blowup guns.