M113A3:
I don't recall the bullet weight that you're using, but for most standard 44-40 weights (say, 200-220 grains), I don't think that a charge of 6.9 grains of Unique is unreasonable. Yes, the powder kind of gets lost in the case, but that is not unusual for smokeless loads in blackpowder cases. You might find it to be a bit position-sensitive (higher velocity when the powder is settled back in the case and lower velocity when the powder is settled forward), but it likely won't make enough difference to really matter.
Of course whenever you're shooting, especially when working up a load, be aware of the sound and recoil of the gun. If either seems light, pause and check that the bullet has left the barrel. That is a common safety practice--you certainly don't want to fire a round when there's a bullet stuck in the barrel.
I say, "Good job in asking questions and thinking this all through carefully." Fools rush in where angels fear to tread.
CC Griff