You've obviously had the barrel out before. Take it out and play the hot air gun on the brass ferrule until you see it smoke, that's the sealant giving way, then pull the ferrule off the barrel. Let it cool, clean up the mating surfaces, line up the ferrule and the dints so that the transfer port will be in line, make a pencil mark on the ferrule and the barrel to indicate the alignment.

Fit the ferrule back on with some thread sealant, lining up the two pencil marks.

The hot air gun won't damage the barrel blueing. Don't forget to take the breech seal O ring out before you heat it all up , though.