This flag defines the amount of damage which is inflicted along the trajectory of the weapon. It is not completely ignorant of armor classes and other properties that can change the amount of damage. In other words, it will obey all damage parameters to determine the damage on the target. However, it is not immune to friendly fire and is ignorant of ownership and does not affect the terrain in any way.
In Red Alert 2 and Yuri's Revenge
This flag is still parsed but it will only work under certain types of weapon. One type of weapon that can be applied are sonic weapons such as a dolphin's sonic waves; having IsSonic enabled and this with a valid amount on the weapon. Another type that can be applied are railgun weapons; as long as the weapon has a valid railgun particle system attached and this with a valid amount.