Had a Kaboom a few weeks ago. Glock 30 with factory ammo. Indoor range. I fired 8 rounds from a 10 round magazine, everything felt and functioned normally. On firing the 9th round, I felt a stunning impact to my hands and face. It took me a few seconds to realize my pistol was now laying on the ground in front of me, and I was bleeding from both hands, forehead, nose and cheek. Fortunately, all the wounds proved to be superficial, the most serous was to my right hand, where the top layer of skin in 1/4" by 1" area of the web between the thumb and forefinger was blown off and powder residue embedded. A small piece of shrapnel 1/8" by 1/3" was removed from my forehead from just under the skin. Both hands were bruised and sore for a few days.
The pistol frame was cracked on both sides, the barrel split in the chamber area, and small parts, like the magazine release and spring were missing.
This pistol had maybe 3-4 thousand rounds through it, all jacketed bullets, never any lead. It had been recently cleaned and inspected, with everything appearing normal.
The pistol was examined by the rangemaster and gunsmith at the scene, and their conclusion was an ammo problem. I sent the pistol and remaining ammo from that box back to the ammo manufacturer for examination. Without admitting any wrongdoing, and claiming they found nothing wrong with the ammo, they sent me a check for the replacement cost of the pistol. In the desire to avoid any legal issues, and being satisfied with their response, I will not name the ammo manufacturer.
Before sending the ammo back, I pulled a few of the bullets and examined the powder myself, including weighing the powder charge. Without knowing what powder the factory uses I can't know the correct amount, but the charges I weighed were in line with powder weights listed in reloading books, nothing approaching a double charge. However, with my admittedly unscientific examination of the powder with a magnifying glass, there seemed to be variation in the size of the powder grains, some much smaller than others.
The only exlaination that I can come to is that the kaboom may have been caused by firing ammo that had been carried in the saddlebags of my motorcycle for thousands of miles. The vibration of the bike, the bouncing around from potholes, etc. caused the powder to break down into smaller granules, which will ignite and burn faster that the would otherwise. I am familiar with this process, as my former occupation was an operator in a coal fired powerplant, and it was well known that different size particles of the same fuel would burn at different rates, and that very fine particles will burn much faster than larger particles.
So, what does all this mean? I know it has been recommended here and elsewhere to rotate carry ammo, mostly to avoid bullet setback due to repeated chambering of the same round. I think here is another reason to rotate ammo. I'm sure this example is an extreme case, and few people will carry their ammo thousands of miles, on a bike or car before firing it. I know any ammo that I carry for long will be used in the next practice session, and replaced with fresh