Sir I believe it is you that is intermingling the two separate forces. Fair enough. Lets test it and see.
Chamber Pressure acting upon the interior of the barrel, chamber and ejecta (and fences) versus a totally separate force called recoil which has resulted from the ejecta being discharged from the barrel with an extreme amount of velocity (Newtons 3d law of motion. Remember recoil is totally independent of and not related to pressure (recoil is related to pressure via the pressure's action on the wad base). Recoil is only dependent upon the mass (weight) of the ejecta and the velocity (which is dependant on the pressure curve) of that ejecta as it departs the confines of the barrel. There is no transfer of the pressure forces outside of the chamber except for the expulsion of the ejecta (and the pressure back thrust on the fences). It is the force of recoil that causes the mechanical actions (back thrust (a pressure force for absolutely sure), torquing of the frame (pressure related), deflection of the barrels and transfer of force from the barrels through the frame to the stock that produce what we are referring to as wear. Lets check what is not marked.
OK, mark-up my respones as you see things.
Suppose we weld a solid plug in front of the chamber and the chamber walls and action are strong enough to contain the pressure. On firing, the chambers will experience radial pressure , which is not related to this discussion. The plug will experience forward pressure which will try to move the barrels toward the muzzle and is relevant to this discussion. The fences will experience rearward pressure (thrust) which is relevant to our discussion. Keeping in mind that force equals pressure times area, we can tell how much force is acting in each direction. The forward and backward forces are combined into axial force. Axial force till try to separate the barrels and the action. The hook and hinge pin will absorb most of the axial force and the locking bolts and bites will absorb the force trying to open the action in a rotational direction. The flexures between the hook/pin and bolts/bites will occur. Any grinding wear or battering wear will occur. The only thing that will not be present is recoil as there is no movement of ejecta, hence no recoil force.
Now, take off the barrels and fit a "sled." Have a shooter shoulder the gun's stocked action and have a helper strike the front of the sled with a maul. The gun and shooter will experience a force exactly like recoil without any pressure.
Why are modern guns not shot loose as often as older guns?
1. Better metal in the joints.
2. Better lube.
3. Less frequency of shooting after an extended storage period where the oil applied to the joint has run out.
4. Less firing to date.
5. Bigger, more robust joints.
6. Cleaner powders, wads, and hulls.
7. More rigirous cleaning and lubing.
