Judging from the appearance of the barrel and receiver fractures, it appears that Sako may have received a batch of stainless steel with excessive amounts of sulfur or with a few sulphide stringers. 410-416 Series stainelss steels use a tiny amount of sulfur to improve machinability, but excessive amounts can produce sulphide inclusions which then act as low-cycle fatigue crack-initiation sites when subjected to high stress.
The fracture, as depicted, appears to be travelling along the same path that metal is displaced during the barrel-making operation and during rolling of the billet from which the receiver is machined. This lends, at first appearance, some indication to what I suspect caused the failures. However, a complete metallurgical failure analysis should be performed to determne the root cause of the failure.
Given Sako's reputation for using the highest standards in manufacturing their products, I'm sure they will do the right thing. :cb2:
