Joda, I believe you are referring to the forward screw on my #86423, which may be replaced by the stud on your gun, both holding what I believe is called simply "the cam". I have been looking for a good diagram of a bar action sidelock, naming parts, but it has eluded me and I'm not as well versed in sidelock terminology as I should be.
Surprisingly difficult to find a diagram of the parts, here's a short video by Wm. Larkin in which the name every part except what I am calling the cam...
https://youtu.be/vO15tbeaWGg 
