Conventional weapons can already do 4200 rounds per minute (ie 70 per second) at much higher accuracy and with much easier reloading. There just aren't that many cases where you need to shoot vast amounts of metal at something, even anti-missile guns don't need more than ~100 rounds to achieve satisfactory Pkill against anything but the most manoeuvrable targets. Most other engagements these days take place at a range where metal storm type weapons are ineffective.

Source: studied weapons engineering at Naval college.

It is but in my mind also kind of pointless. At 1600 barrels and 22000 rounds, you might as well lug around a bunch of RPGs, mortars and laser guided missiles.