Check this out. I have seen this grey, caked stuff in the breech end of a barrel.....was almost like rock. A possible problem could be that your touch hole liner is projecting into the bore and will not allow the cleaning jag to go all the
way down against the breech plug. If this is the case, it will feel like you have bottomed out with the jag, but, in reality,
you are hitting the liner. This is just a possibility, check it out. You can easily check it by marking your ramrod when it
bottoms out and then check this measurement on the outside of the barrel...........Don
I do believe we would all be surprised if we knew how many 'custom' rifles are out there with that problem. Like ol Getzy says check it out. It can be checked from the muzzle as described . Some folks then crank the liner out and guesstimate how to shape the inner end and how deep. I (and maybe I'm in the minority) feel the best way is to pull the barrel and plug and fix by holding the ol gal up to a light and use a rat tail smooth on the end to file her back to the concave shape it needs to be flush with the bore then check her with a patch on a jagged rod to see she passes the liner end with no binding. Better strength that way! This also cleans the grit from your filing away at her!
While I'm acting like I know what I'm doing, listen'read this true tale...! Good ol Mike (I'll take a chance and use his real name which is ________) Ol Mike was using his percussion longrifle at his own shoot and others and had numerous misfires and hangers.
I kept offering him $75 for the rifle and telling him she may look clean but she ain't!! Gotta get that breech clean says I! Get lost says ol Mikey!
To shorten the story, he came to me later (much later) and confessed that he pulled the barrel and plug and had to hammer that fouling rock out of the breech. That rock was over an inch long says Mike. That is impossible says I 'cause the rifle would not fire at all then. Wrong again says Mikey! That rock plug had a fine hole/tunnel straight down the middle and that is why the misfires. Needless to point out that you must soak that breech and not just a little while and get that plug out of there and not let her 'grow'.
I have a seperate rod with a worm attached and I go in there carefully with a patch and twist the thingee and wipe the breech face clean. The ones I build - I polish the face with 400 paper..
My jagged loading rod is cupped and I cut a cross across the face to enable me to go in to the breech at times during a shoot give her a minor twist and withdraw and find the cup of said jag packed with that fouling.... The cross looks like an X so when I seat the ball the ball know where to hit on the target
A word on pulling the breech plug, beware the vent liner may be in to the frt edge of the breech plug so then the liner must be backed out at least part way to pull the breech plug (but you already knew that
)
Well now sorry for getting too long; but hope it helps