I did mean that gunman yes.
Left of center; if you soot up the bites and close it you can see how much contact you have between the bolt and the bites, on the one boxlock gun i have that is left of center if i soot up the bites and close the gun the under bolt closes and makes contact with the back of the bite, the underbolt is wedge shaped which allows that as the bolt and bite wear the bolt bolt moves slightly further forward, the wedge shape compensating for wear, however at some point you will completely run out of wedge toon the underbolt to take up the wear eventually the under bolt will wear out and the gun will slowly become loose.
Dovetailing in the bites or underbolts or decent welding can help tighten a loose action.
You are quite right however, this only applies to certain mechanism in certain guns, most my hammer guns have top levers that couldn't not even move left of center weather the action is tight or loose.
All i mean to say is if you have a gun that feels rubbish and the lever is left of center its possible the action is loose though there are so many factors that affect how a gun "feels"
