Thanks for the reply Silbuster,
I see your point in situations where you have a double +3 on the dice roll, but I've been looking at the Boxer list (SDRS) wherein the boxer musketmen have a +1SV (so I'm down to +4) and if they form a L.Cannon crew, they are down to +3, firing every second turn.

. In these situations, I'm not going to target the chap sprinting across the ground in front of me; I'm targeting the wall/brick/small blade of grass that is stationary in front of him; as long as I can draw a line of sight, I'm taking the easy shot.
Maybe a choice of HE or AP ammo would decide the shooting method.