Thanks for the advice, men.
I dripped Liquid Wrench into the upright chamber with the separated case, and let it sit for about ten days.
I then shaped a dowel and tapped it down inside the case to ensure a snug fit. I was then going to glue the dowel inside the case and tap it out with a rod from the muzzle end, but when I cleaned out the inside of the case with an actone soaked mop (prior to gluing in the dowel) the case came right out wedged on the mop.
Lesson learned: Discard used 30 year old cases even if they look OK. :mad: