FOLDING STOCK COUPLING SYSTEM FOR FIREARM

A folding stock coupling system for a firearm. An openable/closeable hinge mechanism comprising front and rear hinge elements pivotably mounts the rear stock to the main body of the firearm. The hinge mechanism is selectively movable between a locked condition when the stock is unfolded and inline with the main body for firing, and an unlocked condition when the stock is folded forward and offset from the main body for compact carrying or storage. A manually movable actuating button of the hinge mechanism selectively locks or unlocks the rear to the front hinge members in the locked and unlocked conditions, respectively. Embodiments include a detent mechanism for removably retaining the folded position. An elongated rear mounting extension coupled to the rear hinge member provides a common stock mounting interface compatible for interchanging a plurality of different stocks to the firearm each sharing a common mounting profile.