Remove the barrel from the stock and place the breech into a tin can. Prior to placing the barrel in a can, plug the 209 breech plug with an old primer and some tape or something like that then pour some liquid wrench into the barrel so it goes down and surrounds the siezed breech plug. Now you should have liquid wrench or penetrating oil inside and around the outside of the breech. Let it sit like that overnight if it is really stuck fast. In the morning figure out some kind of tool that you can get a hold of it with and put the barrel in a vice. Then with the tool in place tap that breech wrench. That should unseize it, and allow you to turn it out.

I am not sure of the design of your breech. If the plug itself is a slot like a flat head screwdrive or a socket type head. If it is a socket type head, find the right socket and a long extension might reach past the striker area and allow you to turn the whole works out.... I do this with my Black Diamond XR.

The next time you put the breech plug back in, apply a good amount of Breech Plug Grease. After about the seventh shot, take your wrench and turn that breech plug back and fourth to make sure that it is not seizing....