Rookhawk-Regarding your Grulla, how hard do you close the gun? I'm not trying to start another unending "how to close a double" thread but I had a gun that would be very hard to close if slammed shut. The gun operated fine when closed normally, no easing over of the lever but just closed. It usually occurred if someone at one of the local clubs asked to look at my gun. They almost always opened it, then slammed it closed like they did their O/U's. It would almost take a hammer to move the lever. I know the mechanics of some O/U's seem to require a gun be closed with some authority, but some of those guys get crazy with the slamming.
