In on consignment we have a used Winchester Model 50 chambered in 12 gauge. 
The Model 50 was a semi-automatic shotgun using a short recoil action. Unlike most other short recoil designs, the barrel on the Model 50 is completely static. Instead, the weapon uses a floating breech system consisting of a chamber and forcing cone patented by David Marshall Williams; when the weapon fires, this breech moves back about 0.1 inches (0.25 centimetres), causing the bolt to move backwards. A return spring pushes the bolt back forwards.
The weapon was made almost entirely of milled steel components. The weapon's ejector protrudes at a ninety-degree angle from the top of the bolt when the action opens.
The consigner is asking $249.00