According to the story, this guy was reloading, got distracted, and found out the hard way he doubled up.
methodical way of loading ammo. Now semi-auto rifles, shotguns, pistols, ammo loaded for volume, I could see how mistakes could be made. But if you're loading a cartridge for a bolt rifle, precision and consistency should be the name of the game, so every single charge should be weighed, every case measured and weighed, every bullet measured and weighed, I don't see how this could happen. Oh well, not my gun.