I knew that part.The fouling is inherent to black powder.
I've never seen that before. Thx.The period solution was to incorporate a wax wad behind the bullet so that the fouling was kept soft and in check by the bullet scouring the barrel but a constant film remained.
And we're back to my original position: keep the action clean. (I'd have said scour with a barrel brush routinely, too, but it appears that isn't essential.)The fouling needs to be cleaned out by the troops when the opportunity occurs and as son as possible after use but the wax system will allow continuing use.
I wasn't. I was suggesting the solution was the same both times, however.Do not confuse modern weapons jamming through neglect and the routine operational barrel fouling of the black powder military rifle.