Once you get it clean you can use hydraulic pressure to keep it clean. My first longrifle was a Traditions Pennsylvania Longrifle and it uses a patent breech. I still use that same method with my Early Lancaster Rifle from a private builder (was "tg" from the forum) although it has a standard breech and not a patent breech.I started to worry about not being able to swab my patent breech too. Tried a tip I saw on the forum: take a Q-tip and screw it into the end of your ramrod, it's not as good as a brush but at least it'll get in there!
It's really simple actually. Remove your lock and put a toothpick or twig in the vent. Then pour a few inches of water or whatever cleaning solution you like to use (I use MAP) and stand the rifle up to let the liquid soak the fouling while you clean and oil the lock. Then, before mounting the lock back into place, start to run a wet patch down the barrel. As you get part way down you will start to feel some pressure against it because you're starting to try to compress the liquid cleaner and it has nowhere to go.
At this point it is very important that you point the vent away from anything you don't want to stain black that is within about 10-feet of where you are standing. Then keeping pressure on your ramrod, reach down and pull the toothpick out of the vent pushing the ramrod down forcefully and quickly. That will spray out the blackest dirtiest gunk you've ever seen and it will easily spray out at least 6-feet. Anything it hits will be stained black, so don't point it towards a tent!
Then continue to clean the barrel by running wet patches down until they come back clean. When the wet patches come back clean, use a dry patch or two to wipe out any remaining liquid and then finally, run a lightly oiled patch to put a thin film of oil on the inside of the barrel for rust protection.
I used that Traditions longrifle with the patent breech for about 3-years for all my reenactments I did in Vermont and then Virginia before I bought my Early Lancaster longrifle. Using that hydraulic pressure cleans a patent breach out really well and I never had a problem with mine. I never did get a smaller swab or brass wire brush for it and I never needed it. Nor did I need to drill that chamber out any wider.
Twisted_1in66
Dan