Back when I was 15, (I am 47 now) we took a trip to see the family in West Kentucky. Among helping with butter churning and liquor making, I was introduced to shooting BP with a .50 caliber Hawken by my uncle. I liked it so much that he gave me a 1858 Remington replica.
He used genuine BP and he told me to just fill the cylinder, pack in the ball and shoot it. he said, "We only measure powder in a rifle, cause the cylinder will only hold so much..."
In fact, it was many, many years before I ever started measuring my charges in a revolver. I found that I could shoot Pyrodex in the same manner, although I started backing down the charges to around 36 grains (IIRC) in my .44 Remington. That gun has well in excess of 4,000 rounds through it, as we shot up all 4,000 balls Dad & I cast together over the years.
Some days, we had to let the gun sit and cool off before we could reload it.
Now yesterday, I bought me up a pound of Triple 7 FFFg, mainly because it was local and less than $25.00 out the door. But, after reading the label, I'm a little leery of the stuff.
It warns of compressing the charge too much and I always gave the ball a good solid push down into the charge.
So, how much compression is enough to eliminate an airspace and not over-compress the charge????