These are the remains of a 20g Model 12 burst, the center of which is about 6" from the muzzle. I have no information regarding the circumstances or load. My thanks to the contributor.
Muzzle to the right
Major Sir Gerald Burrard in the 2nd edition of
The Modern Shotgun, Volume 3, The Gun and The Cartridge, “The Diagnosis of a Burst”, 1948
"By far the most common cause of burst is some obstruction in the bore, and so the first thing to do is to look for evidence of an obstructional (
sic) burst, that is for a ring bulge. If a ring bulge is detected
the cause of the burst becomes established beyond any shadow of doubt.”
The wall thicknesses just before AND just after the burst were .044". The thinnest part of the bulge was .038".
A segment of the barrel is at METL now for composition analysis and tensile strength testing. I might (later) have them section a piece from the burst edge for additional images, which should show ductal deformation and terminal cleavage, without low cycle fatigue striations. It might also be interesting to EDX any inclusions in the nickel steel.
