Penetration Value and ResistanceThe lowest values of weapons Penetration Value (PV) are based on the scale of damage done to human body tissue, but this scale can be extended to apply to more damage resistant armors. Rather than use the existing body armor classification, I will make a direct comparison between the PV of a weapons round and the Penetration Resistance (PR) of a given type of armor. A round with PV higher than a given armor's PR should penetrate that armor, doing damage to whatever is behind. A round with lower PV will not penetrate that armor, and will do less damage than its rating typically allows. Using the data points:
Constraining a logarithmic function to these points gives me an effective thickness of steel armor plating for a range of PR values. The values I am currently using are displayed on the table to the right. PR for Different MaterialsDifferent materials will have a different relation between their thickness and PR value. Many properties of a material will effect its relative value for use as armor plating of varying thickness, but I will assume a simplified model. Different materials will have a thickness multiplier, allowing a comparison of the relative PR of a given thickness of that material to the same thickness of steel armor plate. For example, common hardwood will have a multiplier of 25 %. This means that a given thickness of hardwood will have the PR of armor steel with 25 % of that thickness.Two inches (50.8 mm) of hardwood will have a PR of 8, equal to the PR of a half inch (12.7 mm) of steel armor plate. Generic MDC material seems to have approximately ten times the damage capacity of high strength steel. This leads me to make the approximation for MDC thickness multipliers: 1000 %. Ten centimeters of armor plate steel will have the same PR, 17, as one centimeter of MDC armor plating. This, like most aspects of this system, is a number that may change in the future, but does seem to function well on the PR scale I've developed. Some thickness multipliers that I've determined (for the time being) are:
PR Used with Human BodiesIt seems appropriate to apply the idea of PR value to a human body, since the original PV scale is defined by a round's potential to damage that human body. Unlike armor plating, humans have both SDC and Hit Points. The potential for complication in this system is great, and many options for use suggest themselves:
When and if these options should be used is difficult to determine. I would say that the first option is appropriate for unarmored characters facing less penetrating weapons, and the second is appropriate for other situations. Developed by Dan Steiner 
