another rather unusual hinge pin system, incorporates centrical sleeves that fit snugly over the central axle pin to provide the bearing surface. if they reach a degree of wear that requires attention, they can simply be removed, and replaced with another sleeve that returns to the desired clearances.
this system was used by franz jager on his verschluss guns, as marketed under the herold name, and licensed to several belgian and other european makers....when these guns were marketed (and parts were available), one turnscrew and 5 minutes could put a gun back on face. a similar concept was patented by j. d. dougall, for the lockfast design - very early in the development era of the breech loader gun....the significant difference being the fact that the sleeve was eccentric (and had to be keyed into the properly indexed position), and thus provided the step-back movement that led to the term "slide and drop" type actions.
i happen to have both a herold gun and a lockfast, and admire the sensible approach taken by dougall and jager to address this situation.
in similar concept, i think of the guns that utilize replaceable rear faces on their rear lumps - so that adjustments can be made "in the circle", without requiring exotic welding and machining techniques.
best regards,
tom
