Major Sir Gerald Burrard in the second edition of
The Modern Shotgun (1948) Volume 3, "The Gun and The Cartridge" discusses the causes of bursts, with illustrations, and inadequate wall thickness, metal flaws, and loading errors are the primary causes of
NON-obstructional bursts. Even with Scanning Electron Microscopy (SEM) I think it would be very difficult to definitively identify the initial failure site as the bottom of a pit.
3 examples of bulges related to over-honing are shown here, and when the barrel bulge exceeds its elastic limit (and other stuff I don't understand) it bursts
https://docs.google.com/a/damascusknowle...nvwLYc-kGA/edit
