Decades back, I would occasionally shoot at a public range that required black powder containers be worn on the shooter and not on the bench or elsewhere. Apparently, they had a horn on the bench cut loose from an errant spark. They figured if the blast was closer, you would be more attentive.
Everything I have read indicates HC was priming with the same powder as main charge. I have read that up until late 18 hundreds, powder was similar to our 2F in granulation....don't know for sure. I have convinced myself that 3F is a bit quicker than 2F in the pan.