So I assume you will try to compress the spring and open the mouth with a drill bit turned by hand ? (or a reamer/ dremel/ conical stone?) So the ball will come out? Refit a spring and ball and pop the breech?
What I did on a Meteor that someone had jammed the plunger in without a spring, was to drill a small hole from the cocking arm slot and knock the plunger out the front with a punch. you wonk be able to see the hole after with the cocking arm refitted.
Once it is out and and you have you spring and ball ready to go back in you may be able to "pre pop" the breech a tiny bit then warm the block and put the ball in the freezer before fitting? Then once it is in a slightly bigger pop or 2?
[B]OR[B] Just buy a Diana 23 or Milbro 76?