Hrm...

Couldn;t that just be a continuous Looping Change in Formation?

I mean a formation could be defined in having the first or two first rows usetheir weapon and then a call to change the formation comes and you have the first row exchange position with the second and then the first row fires.

The firing delay is then not a question of every how many seconds the volley is shot, like the archers, but rather how long it takes for them to re-form, once re-formed then the firing delay comes in to effect.

The complete loop would have to be probably associated with a sorts of "Mode".

Not unlike the Phalanx, which I see more as a mode of fighting rather than a simple formation...

Its a way of looking at it I guess