HB-31 "SALVO"

A turret of guns, fired together, on a single order, into a single fall of shot.
  
  The salvo was the unit by which heavy gunfire was corrected. A full broadside fell at once, threw up a recognisable pattern, and was bracketed against the target by the fall of the next. The technique converted random fire into a search method. The first hit was rarely the first shell. It was almost always the third or fourth salvo, fired after the bracket had narrowed.
  
  For those who understand that the right answer to a hard target is usually a sequence, not a single shot.
  
  Harborborne. Built to Endure.