I spent 35 years at lockheed as a guard. Our guns were company guns that were carried 24-7 by 3 shifts relieving each other. They were handed off to each other on something like 30 separate posts a day. There was a high turn over besides. In those 35 years I never once heard of a AD. I did once hear of a old guard getting through with his rounds and sitting in HQ, out of boredom removing his ammo and dry firing at clock on the wall. Yup, one round went off and he shot the clock about 5 am. Chief came in and he threw his badge on his desk. Chief seen he hit the clock dead center, threw his badge back to him and said, if you had missed I would have fired your butt.
I am sorry if I seem too casual or not serious enough for you guys but when you handle guns that much we dont quite see it as handeling a atom bomb.