Could you snap a pic to indicate where exact the wobble is? Is the whole lens barrel loose, or you just hearing the sound inside?
------------- Alan, I no longer have the lens. I returned it. If you go to Boz's site, there is a photo of the lens. Be sure to pull up the F version. Immediately behind the focus ring there is a narrower metal ring. This shifts back and forth, between manual and auto focus. The wobble is right under this ring. It is the part of the barrel in front of this ring that wobbles. I notice that the FA version does not have this ring. Perhaps it was a weak point. I would guess that the barrel was designed in two parts, and that the parts are joined under this ring. If so, perhaps it can be tightened. Joe

