What's wrong with my Ishapore?

[Vincent]

the chamber is a bit short; a GO gauge will not close up all the way.

I doubt it’s the chamber, Chris. A more likely culprit is the bolt head. That’s because there’s a selection of different sized bolt heads that are used to headspace the rifle.

With a lot of use over time, the receiver of these Ishapores can stretch, creating too much headspace. To rectify the excessive headspace a longer bolt head can be used. A bolt head that’s too long will not give enough headspace.

What you have written so far makes me think it is not a bad idea to follow Peter’s advice. That’s a safe way to go. Your rifle might just need a little tweaking or it might be past its safe useful life.