Some time ago I forget a patch in one barrel of my Kodiak so cap fire never fire the charge.
I pulled the ball.

My sugetion is:
As Sgt sais, get a bullet puller, fix it to a metal rod.
Then tie the rod to a tree or pole and pull the rifle back.
You can "kill the powder with WD40 or other oil throu the the nipple hole but then you have to pull both balls.
Warning!!!! use a muzzle protector.

Hope this hepls.
Martin