Removing Enfield rear sight base

[sleeping dog]

How can I remove the rear sight base from an Enfield No 1 Mark 3 2A1 Ishapore 7.62 NATO barrel? There is one pin through the sight base and through the barrel above the bore. Once that's removed, the sight base doesn't slide off. Is it soldered, glued, painted, shrunk, or just rusted in place?

Regards.

[George Stringer]

Sleeping, there may also be a screw in the rear of the base under the leaf. I would expect these to have been soldered on. I've seen some that have been and some that haven't. George