I've only actually seen two rifles that have come undone, and they were both caused by the ammunition. In one someone fired a 7 mm Rem Express (.280 Rem after someone at Remington had brain flatulence) in a 7 mm Rem Mag chamber that split the case wide open, dumped the gas into the mag well, which blew out the follower and the floorplate off the rifle. The stock may have split. Shooter error obviously.
The other was an M1 that was being fired with surplus British military '06 ammo. A small more or less square hole was blown in the extractor groove of the case which dumped gasses into the mag well and split the stock diagonally through the action. The only damage was to the stock, and since the shooter was walking normally afterwards his underwear was apparently not soiled. The hole looked as though it had been cut with a broach, obviously a faulty case.
In an instance I only heard of, a friend failed to check that his powder measure was completely empty before loading some rounds for his 6.5-08 high power match rifle, and poured in the correct powder on top of the remaining powder. The previous powder was apparently some faster because one round let go and destroyed the stock. The barrel and action (Win 70) were apparently not injured, nor was the shooter except in the wallet.
