meant to say also, unless the bolting parts are truly super finished by lapping etc the initial wear can occur fairly fast, but as the parts wear in & smooth up it slows down as long as it is not abused & kept lubed. his gun was probably built with the cross bolt protruding a bit to the left for the purpose of wearing in & coming flush.
I have two 12ga sidelocks over 100 years old, One English & one German, which were not fitted with wear compensating bolts. Both have double underbolts & a doll's head with the bolts & their bites being parallel to the bolts axis of movement. The lever on both was designed to come to center & stop. Both show signs of being well used but not abused. Both are still tight & on face. The wear on the bolts comes from friction of opening & closing, not from the firing. With these bolts having parallel surfaces when you close the gun the bolt snaps in but literally doesn't touch the bite, having just the barest minimum of clearance to allow it to close. Consequently both have endured for more than 100 years with virtually no wear to their bolting surfaces.
