Echoing the oil friction/pressure relationship:

"Remember to push a dry patch through before you next use the gun: oil in the bore adds extra pressure when you fire the next shot."

https://www.vintageguns.co.uk/articles/practical/266-2/

FWIW, I also think the etching of the bores in a damascus refinishing attempt (not by me), contributed to the stuck wad I experienced here:

http://www.doublegunshop.com/forums/ubbt...5264#Post495264

I guess they call them smoothbores for a reason...