For my "child" load when I'm letting the young nieces and nephews shoot the cap and balls in the yard, 10gr Triple7 3F with a little corn filler or double wad works very well. Whenever using a charge under 15 in these I always make sure to use a known very hot cap. Remington's new ones seem to burn very well. The object of the game here being near instant ignition of every last grain. Anyway, I find that when using small charges the BP subs work best, and I've been doing so for a long time with no problems. Work with your load as much you want to, just always to make sure the projectile whether it be ball or conical is seated tightly against whatever charge you do use. Even if you only use 8gr it will be OK so long as you don't leave any air space. That's the only real problem with tiny charges is the possibility of leaving air gaps gets greater. As long as you don't do that your fine with really any charge you choose.