I tested with someone that saw the same thing you did icepac. While I fired something like 1,000 rounds and only killed 1 gun (that I actually hit), my helper was able to hit something like 6 guns. We are not able to repeat it on a dependable basis though. There seems to be a very narrow window in which you can score a hit, but it involves hitting an area above and beyond your actual target. In other words, it is a difficult thing to do reliably.
Still trying to repeat it.