One poster said that if the plug is stuck the rest of the rifle may be junk but that might not be the case. Old timers never took out the breech because you were not suppose to and they still cleaned the barrel and all othe parts just fine so don't give up on the gun yet. I use to be a big PB Blaster fan but last year Liquid wrench caim out with a new formular which is their best ever. If the LW you have is over a year old go get some of the new stuff.

The next thing I would do if I was you is get a socket, extension and ratchet that fits the plug and use that instead of the tool that comes with the gun.

Good luck let us know what you found.