While pheasant hunting, and having taken several shots, the left barrel of his 12g 1916 Trap Grade burst, and barrels and ribs separated.
He was using older Winchester-Western Super-X, 2 3/4", 1 1/4 oz. 7 1/2 shot. The shot immediately before the burst seemed normal in sound and recoil.
It was not thought to be possible that mud, etc. could have entered the barrel.
Sectioning of a remaining shell from the box revealed fiber wads; possibly dating the shells to the 1980s
The barrel has an about 11" split, starting about 8" from the muzzle. The barrels separated as did both the top and bottom ribs, the bottom rib being bent into a U
THERE IS NO RING BULGE at the muzzle
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There is however extensive rusting of every soldered surface; barrel and rib