you could remove the barrel and soak it? plug one end and scrub.. that way you are not wasting patches?
maybe an ultra-sonic cleaner would help things? https://www.google.com/webhp?hl=en#hl=en&sugexp=les%3B&gs_nf=1&tok=lvJDj_0iy-C_RIUAxUYM1A&cp=30&gs_id=2&xhr=t&q=ultrasonic+gun+cleaner+reviews
I am partial to steamers myself.. when it comes to grease and muck.. hot water is really good and steam is better! http://www.muzzleloadingforum.com/fusionbb/showtopic.php?tid/186740/
I hope that helps.