That is the rear end of the barrel where the shell is inserted.
Near the breech.
Autos and pumps, on the receiver. Over/Unders are undr the breech locking lever
From the breech.
From the breech
Where the shell is loaded.
In front of the butt stock .
Less than $100.
Serial no. C8172
The Darne sliding breech shotgun comes to mind.
The wooden piece under the barrel of a breech-loaded shotgun is called the forend or forearm. It serves to protect the shooter's hand from the heat of the barrel during firing and provides a secure grip for handling the shotgun. The forend can come in various shapes and styles, often reflecting the design and aesthetics of the shotgun.
I'll take it for free :)
Try e-gunparts.com