It is probably stuck from the fouling. They can stick if they are not greased real well or if to many shots are taken without re-greasing it. especially with triple 7. I would put some black powder solvent down the barrel and let it sit, hopefully a little will work into the threads . Then get a wrench and try to back it out. If you can even get a couple of turns then you can add some solvent around the threads and keep going till it comes out. i had a friend that literally had to put his in a vise and strained every muscle trying to get it out. Good luck.