I thought their system required a goodly bit of momentum to operate; they might have to re-size everything in the gun down a bit to work with the smaller loading. I do think a scaled down KRISS would be a lot more practical since they really are a large weapon. Balanced nice and whatever, but it's still a beefy package through the magwell area at the end of the day; a 9mm would be less so.
On the other hand, why isn't there a 10mm version, either? I'd think it would do a great job taming a round that legitimately is difficult for people to control.
TCB