Script to reproduce (requires a vehicle called ArtilleryTarget to be present):
private ["_Target"];
_Target = getPosATL ArtilleryTarget;
CreatedAmmoObject = createVehicle ["Sh_155mm_AMOS_guided", [_Target select 0, _Target select 1, 800], [], 0, "NONE"];
CreatedAmmoObject setVectorDirAndUp [[0 ,0, -1], [0, 1, 0.1]];
CreatedAmmoObject setVelocity [(-3 + (random 6)), (-3 + (random 6)), -900];