Range Modifier
The Range Modifier is a variable that when multiplied against a weapons damage based on distance, it decreases damage correlated with distance (How exactly please add here)
Most ~rifle caliber ammo will have a good Range Modifier . Pistols and other lighter calibers will have a okay range modifier. Shotguns have the most extreme range modifiers.
Equation Hypothesis
[(DamageGeneric * BodyPartModifier)-(Range Modifier*Distance) = Damage Total]