Not sure if this story is true or not but I heard it a long time ago. (This incident happened in the mainland) Guy purchases a 50bmg McMillan or McBros. rifle, shoots factory and reloaded ammo fine. Supposedly the guy buys a buttload of nice and shiny military ball ammo at a gun show. Take the gun to the range to shoot a few rounds, chambers a round, squeeze the trigger, BOOM! receiver gets blown apart, luckily only minor injuries. Pissed guy blames the rifle company, the company request the gun and the ammo in question. Upon arrival a company tech decides to check the ammo, noting the shininess of the military ball ammo. He pulls the projectile out then proceeds to dump out the powder, and finds the powder to be very inconsisent in size. Seems that the seller of the ammo at the gun show, had threw the ammo in a tumbler/vibrator to polish the dull looking ammo. The age of the ammo, along with the tumbling supposedly broke the powder down, there fore changing the burning rate. Well that's what I was told.