SDC vs. MDC
SDC (Structural Damage Capacity) is the amount of damage any item (including living things) can withstand. This is the sort of hardness we are used to in everyday life.
MDC (Mega Damage Capacity) is the result of advanced materials and/or mystic enhancements, to raise the hardness and durability of an object by a couple orders of magnitude.
Mega-Damage attacks (and other effects) are classed as those with the capability of damaging MDC materials. Standard SD attacks (such as a normal person punching a wall) have a completely negligible effect on MDC materials.
Conversely, MD attacks pretty thoroughly ignore the hardness of SDC materials.
In game terms, every object will have two hardness stats, SDC and MDC. They will also have a number of hit points, indicating how much damage they can take. The standard notation for an object is: SDC/MDC (HP). SDC objects will simply have ”—” in the MDC place.
SD vs. SDC—Subtract the SDC from the damage (as per standard d20 damage reduction rules). Any leftover damage is applied to the hit points of the item (or to the hit points of the wearer, in the case of armor). If the damage exceeds the SDC, the item also suffers one point of Wear.
MD vs. SDC—This is the case in which the MDC value is ”—”. No damage reduction applies, and the full damage of the weapon is applied to the hit points of the item (or wearer). The item automatically suffers one point of Wear.
SD vs. MDC—As per SD vs. SDC above. All MDC items have an SDC value, which is generally 10 higher than their MDC value. However, this damage actually represents incidental damage (such as the wearer of the armor getting severely shaken), rather than direct damage to the item. As such, MDC items never suffer Wear from SD effects.
MD vs. MDC—Subtract the MDC from the damage (as per standard d20 damage reduction rules). Any leftover damage is applied to the hit points of the item (or wearer). If the damage exceeds the MDC, the item also suffers one point of Wear.
Multiple layers of protection can be had. However, they must be of different types. For instance, a soldier (with 2/—from the class ability) wearing medium armor (16/6 of armor protection) and benefiting from Armor of Ithan (14/4 of forcefield protection) would have an effective protection of 32/10. However, a fixer with light armor (14/4 of armor protection) that puts on a MDC trenchcoat (12/2 also of armor protection) would only benefit from the better armor, having an effective protection of 14/4. There are two important notes, though:
When benefiting from multiple layers of protection, the damage effectively penetrates each layer in turn. This is important for determining whether or not the armor suffers wear, or the forcefield collapses.
Additional layers of armor may be important for coverage. For example, adding greaves and a helmet to a trenchcoat may not improve the total protection of the armor, but it would increase the CSM of the ensemble. By default, the armor value of the torso is used for piecemeal armor, except in cases where a specific body part is targeted.
Forcefields do not accumulate hit point damage as usual. Instead, their hit point statistic is simply used to indicate their breaking point. If a single attack does enough damage to exceed both the MDC rating (SDC effects cannot typically collapse forcefields) and the hit points of the forcefield, the field will immediately collapse. The field will absorb the damage from that attack equal to its MDC rating, as usual, but the damage used to collapse the field is also passed on to whatever is inside the field. Note: This rule also applies to the field around vibro-blades. If a strike is made with a vibro-blade that deals mega-damage in excess of its hit point value, the vibro field will collapse. The excess damage is typically enough to destroy the relatively fragile physical component of the blade.
Called Shot Modifier
All armor has a Called Shot Modifier (CSM). This essentially represents the percentage of the body covered by the armor.
-0 to -10 — This number is subtracted from any Called Shot attempting to bypass the armor.
@— This represents that the armor completely covers the wearer, making it impossible to bypass.
@@ — This represents that the armor is environmentally sealed, protecting the wearer from most harmful effects.
Most armor values indicate the protection of a complete suit. However, piecemeal armors are also common in Rifts. If a wearer has multiple armor items, add together the CSM of each piece to get the total CSM of the ensemble. If two items cover essentially the same area (e.g., breastplate and trenchcoat), use the greater CSM of the two. If the total CSM exceeds -10, the ensemble is considered to have a value of @. In most instances, the DR of the ensemble will be equal to that of the torso protection. Finally, it should be noted that piecemeal armor can never be environmentally sealed (though it can, naturally, have a sealed helmet with an independent air supply).
ACP — Armor Check Penalty. This modifier is applied to certain skill checks when wearing the armor. Masterwork armor reduces this modifier by 1.
DB — Defense Bonus. This modifier is added to the wearer’s Defense. Typically, this indicates armor that is more or less restrictive than the standard Defense penalty would indicate.
Dur — This is the Durability rating of the armor. See the rules on Item Wear for details.
Caliber — This is an overall measure of the quality of the armor. See the rules on Gear Selection for details.