There is no "back blast". Go to the video at the Metal Storm site (see post #23) and see for yourself. You may not want to throw rocks at this technology after you educate yourself as to what it is.
I was present at the live fire demonstration to the US Navy Fleet Logistics Support Command at one of the Naval Surface Warfare Centers a couple of years back.
I'm not throwing rocks at the possible future applications of the technology, but neither multibarrel launchers nor linear propellant/projectile stacking within those barrels is a *new technology.* And I an quite aware of what it is.
But you might want to be more aware of where it can be heading.... and the marriage of the Burney recoilless principle with the Metalstorm electronic sequencing of ignition offers some near-term practical applications.
-archy-/-