Here are a few pics for you.
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In this pic you can see what the barrel actually pivots on and is held in place by. The grove in the barrel lug rides on the large pin in the reciever. Indicated by the letter A in the picture.
It is held and locked into place by the lever in the back of the reciever and the notch in the back of barrel lug. Indicated by the letter B in the picture. This is what moves when you press the button to open the barrel. It's sort of like a simple trigger really. This is actually a pretty strong, simple and solid design.
In the next picture you can see that the plastic peice on the grip really just helps guide the barrel and fore arm around the reciever and helps hold the barrel in place when the breach is open. When the gun is closed and locked it really just serves as a piece of trim to fill the gap for looks.
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These guns do use plastic on them and the fit and finnish leaves much to be desired. However they are plenty functional and priced very well for what they are. If they had all metal trim and smooth polished surfaces they would cost much more to make and in turn would cost more to sell.
This would make it hard for them to compete with Mossberg and Rossi. I do wish they made a Premium series or something that had nicer trim and finnish. I think many second time buyers would pay the extra money for it now that they know how well they perform.
Paul