I've had one ND myself, after cleaning a .22LR semiauto gun of some kind, don't remember for sure, but it was probably one of my junk Erma ones. I had cleared it, cleaned it, and then, probably because it was really late , like 4-5am, and I was too tired to be doing anything with a safety risk, I put the mag back in, racked the slide, and pulled the trigger. BLAM. It seemed louder than I thought was possible from a .22. My mother was living with me, and somehow, it didn't wake her up! The bullet went through a rug and about a half inch into the floor. My dogs took off, one was in the room, the other one was in my bedroom next to the room I was in. I was genuinely shocked when it went off. After I calmed down, I went to bed, and never told my mother she had slept through it. After that point, no more ammo handling of any kind that late (My normal bedtime from birth is about 5am) at night.