One of the surest ways of geting a gun off face, is not as common as once was. This was forcing swollen paper cases into the chamber by closing the gun with the hinge improperly lubed at the same time. This put great pressure upon the hinge while it was in a rubbing motion. Much worse than however hard it can be slammed without actual pressure against it. Of course if the forend has a heavy spring forcing the bbl hook against the pin, it always has pressure against it. Also ejectors which are cocked by rubbing down the breech face puts pressure on the hinge.
"Love Those Lefevers"
Very few guns are put off face by actual firing, it's the frictional wear in opening & closing.
