I have a beretta pintail 12ga. with 26" barrel and its my faorite duck gun.like abig dummy,about 3 years ago i?

was out of choke lube and put bore butter on threads.,now its froze tight and i mean tight! ive tried soaking it for aweek in penetrating oil,no good.itook it to a part time gunsmith,and using gun smith is being polite. he wanted to send it off and have 2"cut off my barrel,its a 26" barrel ,ribbed! of course they don't make this gun anymore.i pulled up a used barrel-450.00! ive trieheat,and everything else i could think of,nothing.ive broke 2 choke wrenches,and just don't know what to do .as you know ITS amod. so ican shoot steel shot and sooner or later ill shoot it out and have to replace it.how can iget this choke out.please help.