How to get a 30" grease worm out of a barrel? What'll happen if I google it?
I say take the wood off said shotgun and bake it in the oven at 500 degrees f. until the ball comes free of the barrel (or vice versa). Time it with an egg timer, make sure the wife is out of the house (it may smell bad after the discharge in the oven) and take a time laps video.
For a clean up (if there's anything left over), you guessed it...straight to the dishwasher with that bad boy. Lots of hot water and soap.
Don't use heat to get the charge out of the barrel.
Man At Arms magazine editor told a story of a friend that had just purchased a gun in the same state as you have, and in the process of melting the bullet out of the gun, shot himself with a civil war era muzzleloader!
After being taken to the hospital, the police showed up, because the hospital MUST report every gunshot victim to the police. So, in addition to accidentally shooting himself, he also had to fill out a police report, to a couple of officers who had trouble not laughing at the poor guy.
The grease gun sounds like a much better solution to your problem than using a flame, even if it is just a little one.