Somehow, despite being careful, I've a managed to get a bit of grit into the butt end of one of my scopes. While with a bit of shaking about I can get the rod to extend properly, it's a bit of a nuisance and I'm sure the shaking and scraping required to get it to extend can't be doing it any good.

Anyone know of how to fix this? Is it possible to pop off the cap at the end of the but of the rod to clean the internals?