Al. I just tried to look on the Chambers site to see if the parts diagram might shed some light on this, but can't access it on this ageing I-Pad!

However, I just put "Weihrauch HW25 barrel detent" into a Google search. Came across the diagram on the Knibbs site, clearly showing the ball and spring. So you assume not a "sealed for life" affair and you should be able to access?

Might be worth pursuing the search on the web a little. I'd have a look for you but running out of time....

Hope you sort.