Alfred: shotgun barrels have no moving parts, though there is some flexion with the shot and expansion with the ejecta.
Properly designed and fabricated barrels, using metal appropriate for the application, subjected to pressures for which they were designed, do not weaken over time...well, maybe in a few thousand years
The problem of course is corrosion, pitting, obstruction, and using shells for which the barrels were not designed. None of us can know the abuse our barrels may have experienced before we acquired the gun; but a bore gauge, bore scope and wall thickness gauge and help.
Frank: how can you know that a boxlock stock head split down the middle wasn't caused by excessive recoil?
THIS certainly looks to be from trauma
