First of all I've seen this before and would not exactly call this "new" technology. The fact that this has been in experimental stages for so long tells me that not too many people are impressed.
While looking at the video the people talk about all the uses of this weapon I think that most of the attributes also apply to many conventional firearms.
Rapid fire: I noticed that to get the high rate of fire claims they stack a bunch of these weapons together. I suspect a bunch of M2s stacked up and fired in sequence could get an equivalent rate of fire.
Three shots, one recoil: I remember reading about a future military rifle that did this. It had three barrels on it and fired a sequence of three sabots with each trigger pull. I think it used mini-rockets or some other kind of caseless ammunition, it wasn't MetalStorm. Oh, and I read about this somewhere around 20 years ago.
No jams/misfires: A Gatling style weapon that is electric or hydraulic powered is not likely to jam or misfire. A round that fails to fire will simply be ejected with the spent casings. Now, a round that is stuck in the barrel may not exactly be pushed out by the following round like in MetalStorm but the chances of a round firing and not making out of the barrel is quite small.
One major concern I have with MetalStorm is the accuracy. I see that when multiple barrels are mated together they have a very small group down range. I also see that a bullet from the same barrel is going to hit the same point as the bullet preceding and following, which is to be expected of any modern firearm. What I'm concerned about is the accuracy when used on small arms.
In the case of a handgun the accuracy may not be of considerable concern. It just has to hit MOBG at the length of about 7 meters. In the case of a CIWS/Phalanx/Goalkeeper type of automated system the bullets are tracked by radar and the computer can compensate for an inaccurately mounted barrel.
What about a M16 type weapon where a warrior is expected to make a kill at 300 meters? Let's assume the barrel is loaded with 10 rounds and a set of four barrels is mounted in one "magazine" that is intended to be switched out. So a warrior goes out to the range and sights in the weapon, and in doing so fires off ten rounds. This poor defender of all that is good has now expended one of four of the bullets in the magazine, only to have to sight in the next barrels when the other 30 rounds have been expended.
Now you also have a warrior carrying around not one barrel but one barrel for each 10 rounds of ammunition. That is going to be very heavy unless the barrels are made of some exotic materials. If the barrels are made of something like carbon fiber to make it light then it's going to be very expensive.
I don't see how this is going to be practical in any but a very few applications.
