Did the frame Stretch, or did the hinge pin bend or the steel in the barrel lump compress? Was the rotary bolt Not Fitted so as to help carry the load. How much difference is there in the strength of a 20 ga Fox frame & a 12 Ga one?
All of these factors have to be considered to say it was from Shooting the gun.
In the automobile engine, the parts as stated are constantly Lubricated. Leave the oil out of one & see how far it goes before a total lockup.
I did not positively state this was the cause anyway, only offered it as a "Possibility". You can think that frictional wear is an impossibility in the hinge joint of a double if you choose to, but I seriously doubt you can prove your case.
