I was at a sniper competition over the summer and at one of the night events, my weapon mounted night vision failed. I had to switch to a head mounted unit for the remainder of the event. Because of this I was scope bit every time I fired. Unfortunately, there was nothing else I could do, besides forfeit the event. Result: 8th place in the event, black eye for 3 days after. Lesson learned: Make damn sure your batteries are charged, or at least interchangeable. That was our fatal flaw. The weapon mounted took AAA while our head mounted took Surefires.