The way i read it is this, he took the rifle to a couple of shop who both said it looked like chamber failure, based on that he sent the rifle to the manufacturer to inspect it and test to see if it had any manufacturing flaws. I don't see that he straight out blamed the manufacturer, he just wanted a definitive answer as to whether or not there was a fault that contributed to the failure. If he did not tell them that he was using hand loads and especially someone else's hand loads i can completely understand that. Telling them it was a hand load brings the instant assumption that the hand load was the cause, what he wanted was for them to inspect and test to determine if there were any flaws in the metal that may have contributed to the failure. Yes it was probably the hand load that caused it, but did it happen because there was a flaw that failed when the high pressure round was fired and that if that flaw wasn't there it wouldn't have blown up?? He's like me in that he wanted more information not just someone saying that it was the hand load. Bear in mind that the information about the hand load being a mixed powder charge was only discovered during this thread and not known at the time of firing.
Also i have seen comments saying that he Blackmailed the manufacturer, you have no idea what was said between him and them, you just automatically assume that because he has pics and video of it blowing up that he must be trying to blackmail them into giving him a new rifle. A lot of assumptions being made on here.
In engineering, we use safety factors, i.e. Calculate the strength of a given assembly, then apply a safety factor of 2, and tell the customer that it's safe for half of the calculated strength. We KNOW that at some point, everything will fail, it's a fact of design and engineering. We also know that calculations and manufacturing are not perfect, they're subject to tolerances and material variances within reason. The point of the Safety Factor is to ensure that the product will not encounter a mode of failure under any reasonable circumstances.
In a rifle, the action and barrel are rated for a certain level of pressure within the chamber, the rifle is built with a calculated safety factor to withstand pressures in EXCESS of SAAMI specs for that caliber. Depending on how each component of that rifle is built, it will withstand a certain amount of pressure above and beyond SAAMI spec, but without encountering a failure and knowing the pressure of every single round fired, nobody knows where that limit actually is for any one rifle. For liability reasons, before each rifle leaves the factory, a proof round loaded to SAAMI max pressure is fired, and the rifle is inspected, to prove that each rifle is safe for the end-user to fire. This process is documented and kept on file, so that if something like what happened to the OP occurs, they have sufficient legal proof that their product was safe when it left their factory. Through their inspection process, they KNOW that each rifle they ship is safe to fire with ammunition that is within SAAMI specs for pressure.
Somewhere beyond this pressure, SOMETHING will fail, though it won't be the locking lugs since they're engineered to be the strongest part of the system, preventing you from being impaled by the bolt if you do something like the OP. On the OP's rifle, let's say the rifling was cut slightly too deep, and the barrel split there, at 1.5 times SAAMI max pressure. Or, maybe the OD of the barrel was cut to less than the minimum tolerance, and the chamber was was thin, causing a split failure there at 1.4 times SAAMI max pressure. Maybe the threads were cut too deep and the barrel failed there at 1.37 times SAAMI max pressure. Heaven forbid, maybe all of these manufacturing flaws were present on the OP's rifle, along with an improperly heat-treated barrel blank, and everything failed - at 1.2 times SAAMI max pressure.
So then, 10 gunsmiths inspect the rifle and determine that the failure occurred where it did because of all these things; it's still irrelevant because the round was loaded above and beyond the maximum rated pressure. Whether the same load has been fired 100 times in his friend's rifle is irrelevant, because that's a different rifle from a different company with different specifications. If that Remington blew up too, the OP and his friend would still be at-fault because the load was improperly loaded IN EXCESS OF THE MAXIMUM RATED PRESSURE FOR .338 LAPUA. End of story. Savage had proved that this rifle was safe to fire long before Fenix Mike took possession of it.
-matt