t1958 - don't agree with you on a few points. The tendancy for the action to open is due to a torque around the hinge pin created by the backthrust of the fired shell being above the center of the hinge pin. The resistance to opening would have to be a torque in the opposite direction. It would be composed of the force applied to the locking mechanism times the distance from the hinge centerline to the center of the mechanism contact area. The longer the distance, proportionally the less force applied. However, strength in this case is ability to resist shear force applied to the locking parts. Shear stress on the lock parts would be opening force divided by shear area. Strength of the action, then, would depend on the relation of the shear stress to the strength of the alloy of the locking parts. A locking mechanism located a long ways from the hinge pin might be either stronger or weaker than a Purdey bolt depending on the size of the lock parts and the strength of the alloy used.
