I'm just guessing here, but my speculation is a patch of whatever cloth they had handy smeared with whatever grease they had handy.
For
sure it was not this. Greased cloth was like all of the other load components in the British BPE rifles at the time: Exhaustively researched, carefully documented and tested, flawlessly functional. Nothing random about it. I wish I could upload photos to this site from my computer, because some of the rifle case labels have intriguing descriptions of the greased cloth they used. There's an 1880s Charles Lancaster rifle case label that describes the greased cloth as a "perforated green cloth," as though it were a felt wad with holes punched in it, dipped in grease. I have been experimenting with different types of materials, and one thing for sure, these wads were pretty thick, like 0.07" and thicker. Graeme Wright describes what he found inside the BPE cartridges: "a grease/ wax type wad." When the powder did not fill up the case, then these components had to be stacked upon each other until the air space was filled and the bullet could be properly seated.
Anyhow, inquiring minds want to know...
thank you!
