I am unaware of any pin in the Martini Henry or Francotte Martini that could wear so much, and still function, that it would effect the action staying open or closed.
Action locking is caused by a combination of the horns of the lever and the goose neck of the tumbler. Both of these parts mount on the same pivot pin in the lower rear portion of the action.
In the MH they mount on the cocking indicator shaft. In the Francotte action they go on a simple pivot pin.
So the question that needs asked first, which Martini do you have.
A Martini Henry style with all the parts mounted to the action body or the small Francotte style Martini where the parts are all mounted to the trigger group and slide in the bottom.
This is a Martini Henry style action
Note the hinge pin to hold the breech block, the cocking indicator pointing straight up, and the front extractor/trigger guard screw.
This is a Francotte Martini
notice the only pin or screw going though the action is the front take down screw, that holds the trigger group in.
Can you take pictures of the worn parts you are referring to.
