Never happened to me (knock on wood), but a buddy put a 5.56 thru the roof of his house. Since then I always tripple check my guns whenever I touch them. Even if its pull it out of safe to check something, its pull it out, check to make sure its empty, do whatever I needed to, check again to make sure it didn't spontaneously load itself, check a third time, dry fire in a safe direction, and back in the safe. Same thing for at the range when shooting. Fire off mag, check chamber, check chamber, dry fire (all this while pointing down range), then put in case. When I get home before cleaning or putting in corner, check chamber, check chamber. I may know the gun is unloaded, but the day I start counting on that is the day a hole appears in something.