I am in the same boat as you, the kit I am working on is missing the patch box cover, ram rod pipes, sights and trigger guard so if you end up with any extra parts once yours is completed give me a holler.
I will give that a try, I ended up pulling the breech plug last night and working on getting in cleaned out now. Part of the problem is fouling and rust down in the barrel that I couldn't see from the muzzle end.
Any idea for a jag to clean .300 smoothbore everything I have tried either gets stuck on the back stroke or looses the patch. I'm thinking about some 30 caliber mops but not sure if they would leave the bore dry enough between shots