Well for a start with an artillery strike we would be discussing spread ratio or saturation ratios not "spray" Spread ratio would control the distance covered by the strike so the spread could be a 5km target surface area or a 100km area depending on how much spread you need. Saturation ratio is the intensity of the artillery strike, are you looking to suppress enemy troops with lightweight munitions or looking to literally reduce everything including the hills to nothing? Even with the accuracy ratio to maximum errors possible the missiles all strike home dead on target in the FMV. What I find weird is that they have individual on board targetting computers as witnessed by the mechanical eye on the missiles in the FMV the only thing what made them miss is the fact that Garden moved.