yup, it's as simple as quickdtoo says,,
Them small bores is finicky,,an sensitive too foulin,but it ain't likley bore fouling thats causin them "snail breech" TC's ta foul. It's the nipp's and caps.
I don't care what "caps" yer usin,,them things foul worse than powder nowadays,
,,ever heard of a thing called a "nipple pick"? It's just a little piece of wire that pokes through that little hole in the bottom of a nipp? You go ahead and swab or not, and load that main any way you want. Tap the main into tha fire channel, then pick that nipp. You'll feel that "crunch" just like rock tosser's pickin vents if you load proper,,
Look at it this way,,it's really hard to not get powder to go off if the "fire' get's too it,,,