I thoroughly cleaned my barrel, scraped the breech too. Also the vent liner. When I got done, I stuck my tiny bore light into the vent hole. (Light from a night fishing bobber. To my surprise, it looked like the light was ahead of the patent breech cavity. I have enlarged my vent liner hole to 5/64.
I have the original lock on my TC, it sure may be contributing to the problem, as it eats flints. I will search for a 2nd generation lock. I’m going to continue to wipe between shots, but use the correct jag and patch.
I also live in Georgia, and high humidity is surely adding to the problem.
I’ll get it sorted out and report back.
Thank you all for the tips and advice.
I will also go back to spit patches for a time to see how effective it is.
I kinda stopped reading when suggestions swung to Percussion lock issues where you are clearly working with Flintlock, as you mentioned the vent liner in the very first post...
Anyway; I wipe between shots too but I don't use Dutch's system (bought the book, read it, but never tried it).
However I had some time back had the same issue you described.
1) First time, I had put maybe 1000 plus shots through my new Pedersoli 50cal.
I Always remove the liner when I clean and I clean it too, so I know what it looks like we'll and when my miss fires and began looking for "Why?" - I swore the vent liner looked 'different', the hole looked larger (never measured it) and the inside just looked 'different'.
So I purchased a replacement and replaced it...problem stopped.
2) Then it came back (misfire with flash in the pan); I first suspected the line...but it looks like new still?
Then, I don't know who but I found 'crud' was building up and apparently blocking the vent hole, maybe after 5, 7, 8 or so shots - even with wiping.
So, I found that after every wipe or two I turn the rifle upside down and Slap It and out fals a few bits of shmut....misfires stopped.
That was a few years ago.
In closing; while your shooting and wipping- After a wipe turn her muzzle down and smack her, see if any blackened bits fall out?
Also, when I load my powder I always rest the but on my foot, tip the rifle and Slap it so I settle the charge AWAY from the vent (lock) side. I know many just bounce their rifle on the ground to settle the powder but I like to settle mine Away from the vent, and yes I have noticed some at club shoots kinda lookin funny at me - or maybe it's because I am the one yet to have a misfire at our monthly shoots...