I recently purchased a well used Model 1200. About every other time I try to cycle the action with a spent shell or live one, it jams shut.

I figure something is worn out and needs replacing but I have no idea what. I have to hold the shotgun by the forend/slide and bang it on the ground to clear the chamber.

I thought the chamber might be rough and causing too much friction, but it is nice and smooth.

Any ideas?

Thanks, Monte.

There is an internal screw in the action that can loosen on the Winchester 1200 if the gun is used heavily.  Remove the trigger guard assembly (includes the trigger, hammer, yadda yadda) via the push pins and examine it.  If I remember correctly it is the screw through the shell elevator (it pivots on it) that can loosen and gum up the works.

I haven't had a 1200 in years but this happened to me.

Cheese

Before I forget also disassemble the bolt assembly.  There is a screw in there as well.  

Sorry I can't be more specific, but it has been a decade or so since I had a 1200.