Priming powder, air compressor or the two curled wires-design patch puller will get it out. I did it a few times in my percussion barrels. The worst thing to see down there is an unscrewed bore brush. That takes double-priming to push out....lol [X(]

None of those pictured above is a 2-wire patch puller. The 3rd one on the left is close & may work. I did'nt like mine. It's still in my tackle box collecting dust.

The one I like (2-wire) is in this picture below. When you reach the breech with it, do not use pushing force. Just turn it clockwise a few times & pull up. Putting force on it will bend the wires. Believe me I know -- I broke several of them before I got smart.

http://www.traditionsfirearms.com/eshop/10Expand.asp?ProductCode=RM9013