the million rounds thing is never going to be used. They fire it for a couple milliseconds to get the results they want.
I don't know what you mean, blehm. They can't possibly carry around one million rounds and they certainly wouldn't expend one million in one volley. I don't even thing they have anything capable of containing one million rounds. The idea is that they would fire a burst over a large area, like a split second minefield. It's actually envisioned to replace mines in some respects because there is much less danger of killing civillians and there is no trouble finding them once you have installed them.
Like I said, the one million rounds per minute is a measure of cyclic rate. No M-16 has ever fired 900 consecutive rounds in a single minute- it's just the measure of how fast the mechanism works.