Well the blame is on the manufacturer if they did something wrong, obviously. If they made the gun shoddily or incorrectly and that caused it to blow up, then they're at fault. Same with the ammo manufacturer if they loaded the wrong cartridges.
There's stories of getting .44 Magnum in .44 Special boxes. While most of us would see it and say "Hey that's not right!" there isn't much we can do if it's stamped correctly but loaded wrong.
If you hand load, that's on you obviously.
Massachusetts Native (Tough to be a gun owner!)
Owner of: S&W Model 10-5, Beretta 92fs and a Mossberg Maverick 88 "Security" Shotgun