Remove the front sight bead.

If it is a clay gun shoot it liberally onto the threads with carb cleaner. It very well could be hot plastic from the wad and it got behind the choke if shot extremely hot.

Soak as noted with intermediate heat (make sure and not use an open flame), think heat gun. Some of the penetrating oils will catch fire.

Make sure the threads are actually in the oil.

The soaking may take a week or so.


Lock the barrel down in a barrel take down tool, even if it's used for rifles but something that has aluminum or copper sleeves and then locks down, wrap painters tape even so.

Finally
leverage get a piece of pipe that you can slide over the "T" handle. Gently but rapidly begin to tap on the end of the "cheater bar" acting like an air wrench it should break it loose.

Once out get a drill attach a copper cleaning brush on a rod and your favorite bore cleaner and just clean the crap out of the inside of the barrel before cleaning and reinstalling.

I'm with high strung with getting the extended tubes do allow for constant checking when shooting to keep hand tite, but also allow for more vigorous removal methods if something does get stuck.