Ready for way two much verbiage for my two cents worth? Most of the rifles I played with using black powder benefitted from some compression. They ranged from as little as a 1/16" to so compressed that the powder charge became a nearly solid plug. All learned by experimenting trying for best accuracy. Better grades of BP seemed to be the most tolerant of the least compression. Those would be Swiss and Olde Einsford. Less favored varieties needed more crushing.
I always use an appropriate compression die and I like a thin, laminated hard paper wad under the bullet. The card is already in place when I run the charged case into the comp die. The exception was cowboy ammo where I cut felt wads out of old hats and soaked them in melted Crisco for extra lube trying to keep a gun running for more stages before needing to be spritzed with 1 to 10 Ballistol and water.
I think there were three of us playing with 11/84 Mausers and their voluminous cases. They gobbled up lots of expensive BP and kicked like mules. My buddy Mick came up with grinding Rice Crispies and dehydrating them as a case filler to get the charge down to a manageable 70 grains or so. I tried duplexing my 11/84 to reduce fouling. Holy Mother of God, the muzzle flash was nearer white than orange and louder than hell. The recoil was ferocious with a 10% BP reduction sitting atop some 4759.
All of my odd ball BP cartridge rifles like .43 Spanish and Egyptian Rollers are gone, the Mausers too. There a C.Sharps and Shiloh Sharps left in a couple of more mundane calibers, well one is a .40-70 SS, but still pretty straight forward.
The bottle necked stuff seemed to need less compression, but out of all of them, the only one that produced truly impressive accuracy of actual 1 MOA at 200 yards from seated cross sticks, was the more mundane .45-70 in the Shiloh Sharps, using every trick with the bullets and ammo I could conjure up. But I did get away with a blow tube and did not have to wipe between shots for up to 8 rounds. Over that and the groups started to spread like Rosie's back side. Oh God, I just re-read that and I used wipe and Rosie's back side in the same paragraph. (Shuddering on my way to the coffee pot.)