The C4 ammo analogy is not quite valid. A shot will either be safe or blow up the gun. But each of those SHT Springfields passed proof at the factory, and may well have fired hundreds or thousands of standard rounds since.
Yet one shot, one day, may blow the gun. There is no "controlled environment" non-destructive test that will determine when or if that could happen. The steel can be sectioned and examined under a microscope, but that ruins the rifle. Or extra heavy proof loads or special "fast" loads can be fired. But failure means a ruined rifle.
Myself, I would rather own a nice old M1903 that I won't fire than own a box full of broken steel and splintered wood after a "controlled" test.