Cool !!!!!!   Thanks for the link, Finn45.

I tried zooming in on the split barrels to examine the metal surface, but the picture was too grainy.   As near as I could tell from the grainy pictures, the failure began about 2" in front of the throat, which is where peak pressure would occur in a normal load -- so nothing unusual there.   What is unusual is that even the receiver split in two.   Best guess is that the barreled action missed a tempering step, so it was as brittle as glass.   A softer metal would have the classic bulge at the point where the failure originated.

Yep, shit happens even in... But don't know really, most contributors here in F are suspecting sabotage pretty heavily and have to admit that three petaled case just looks little bit too handsome. What ever it is I hope that Sako, Federal or some third party is asked to find out the reason. Anyway I think that any obstruction, bullet, jacket or lost cleaning jag would most likely bulge the barrel somewhat. This seems to be quite popular topic around the gun boards all over the globe btw.

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Sorry Joe I don't recall Esa Verho, but must say that name sounds just a bit familiar... maybe seen it in some Sako brochure or magazine article.

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Wouldn't the action and barrel be tempered separately and differently?

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Yes.   Come to think of it, aren't those barrels made by the rotary hammer method?   I wouldn't think they would receive a heat treatment at all.   It doesn't make sense, does it?   Yet clearly the metal was brittle.

Starmetal, if the metal was brittle then the fluting would indeed act as a stress raiser.   Fluted barrels are incredibly stupid.   Varmit Al's website has a nice analysis debunking the popular myth that fluting makes a barrel stiffer.   Besides reducing stiffness, cutting the flutes creates residual stress in the metal and weakens the barrel as this incident clearly shows.  

Hammer forging cold works the metal, making it harder but less ductile.  The barrels might receive some kind of stress relief after the hammer forming process, I'm not sure. 

What is different here is that there is no bulging or peeling, and the fractured surfaces have a crystalline appearance except at the point 2" in front of the throat where there is some tearing (probably where the failure initiated).  Brittleness would be my guess.  A metals lab should be able to verify that, but we'll probably never hear the test results.

One other theory -- and it's way out there -- is that the fracture may have started near the muzzle due to a secondary pressure spike.   The flutes, acting as a stress raiser, then allowed the barrel to split all the way back to the receiver, like splitting a piece of firewood.  Even if it did happen like that, it doesn't totally explain the straight, crystalized fracture.  

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The only time I would have barrel flutes is to balance the rifle for offhand.  Just chopping the barrel off will do the same in terms of balance for me as a charging tin can person, but a true offhand competitor would prefer a longer barrel because of its better recoil control. You don't see flutes on a BR gun, and that's because your doing nothing but chopping out the needed weight for the recoil control.  Flutes make the cylinder/barrel weaker.  Whoever started the strengthening myth should be flutted. ... felix

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