The_Dunedan

I've seen KB-ed rifles like this on two occaisions; I was not present for either accident, but I did get to see the results when the owner brought the gun into our shop to be rebarreled. Sako, which is a -very- reputable manufacturer, had to recall a large number of their rifles about three years ago because of a metallurgical fault which was causing this kind of thing to happen. And you had better believe those pieces of steel were -razor- sharp. I also know of one person who had a National Match M1A destroyed like this; still don't know what caused it, but it wasn't a barrel obstruction.

And yes, that is how high-tensile steel behaves in an explosion. The Savage barrel in the second set of pictures is what happens when the chamber/reciever is destroyed by some malfunction in the rearward portion of the barrel; the OP was caused my an obstruction near the muzzle, which prevented the metal from "tearing" all the way back to the chamber. If you look closely, you can see how the "petals" of the barrel are re-curved near the muzzle: that's because that area was where the pressure behind the bullet first exceeded the strength of the barrel. Sometimes, especially in shotguns, a small obstruction will be enough cause the barrel to bulge (some gunnies call this "jugging") but not to rupture. In rifles, because of the -much- higher pressures involved, an obstruction of the barrel usually results in this kind of thing. Oddly enough, a frequent cause of this kind of accident is some numbnuts sticking the muzzle of the gun into some water. The water can't compress, and all that expanding gas has to go someplace...and kablooey she goes. Basically, a sudden, dramatic increase in chamber/barrel pressure is a death-sentance for a modern centerfire rifle.