"...like on rifles..." That'd be too easy. What does the 'pin' just aft of the stock screw do?
"...the thing just stopped..." Where? Mind you, I suspect Clobbersauras is right. Pull the trigger.
You ever looked at a VZ-25? The Rhuzi is based on it. Looks a lot like your Rhuzi. Mind you, I can't find much other than pictures.