from the uspto right on schedule, page-5

I finally got hold of the PDF for that patent CJ, in it they are talking about using metalstorm electronically fired stacked round technology on a guided torpedo, they are using an open ended tube in which there is a projectile that is fired at the target and another projectile that is used to minimise recoil.

The projectile with the pointy end in the diagram FIG1 fires at the target at supercavitating speed, when it is fired another projectile fires in exactly the reverse direction to the one fired at the target, the two combined recoils cancel each other out, this is absolutely necessary on a guided weapon such as a torpedo, otherwise the recoil would cause it (the torpedo) to be pushed off target, but you could just as easily use this same principle in a guided missile.