I was watching a youtube clip of most of the cell phone videos and I'm pretty sure this guy was using drum magazines. Assuming it was an AR15 or some variant, a regular stock clip on full auto will be gone in about 2 or 3 seconds of steady firing. I know this because I've done my fair share of shooting full auto assault rifles. This guy was going for about 5 to 7 seconds without reloading.
And it wasn't a belt fed weapon (like an m249 SAW), because the firing would go on a lot longer than 5 seconds, and would take longer to reload.
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