[d20 & D&D 3.5] Armour as DR variant

[Altair_the_Vexed]

Here's relatively big idea - please have a look and let me know what you think.
I'm not confident I have assigned the protection types of the armour very well - my common sense approach may be wrong to someone with more hands-on or academic experience in fighting - so please make counter suggestions!

The normal d20 game (D&D, d20 modern, etc) deals with the idea that armour makes you harder to damage by effectively increasing the difficulty of scoring a good hit on an armoured target: armour simply increases the number needed to hit. It's a bit simple, and doesn't take into account the many different weapons and armour combinations that exist.

The OGL (http://www.opengamingfoundation.org/)product Unearthed Arcana included rules for treating armour as damage reduction (DR) (http://www.systemreferencedocuments.org/35/sovelior_sage/abilitiesAndConditions.html#damage-reduction) - wearing armour gives you some bonus to defence, but also reduces the amount of damage you take. Typically, the armour bonus of the armour (from padded armour's +1 to plate mail's +9) is evenly split between AC bonus and DR. Characters get hit more often, but they take a little less damamge each time.

Now, one of the early ideas that disappeared between editions of D&D was that different weapons had advantages over different armour types. Chain mail affords less protection against a mace than it does against a sword, because it flexes with the blunt blow, for example.
This is especially relevant to modern armours - a kevlar vest that can stop or reduce the penetration of a bullet is next to uselss against knives.
I thought it might be interesting to work on a system that deals with this, using the Armour is Damage Reduction variant from Unearthed Arcana. Damage in D&D and d20 systems is already classified according to the type of weapon or magic you are using, so it only remains to decide which armour deals with what kind of damage best.

I came up with this list of protection types.
acid (abbr: Ad) - Material resistant to acids, alkalis, etc, e.g.: hazmat suit ballistic (abbr: Ba) - A mesh or gel or other high-speed impact spreading material, e.g.: flak vest bludgeoning (abbr: Bl) - Padding, often with a tough outer material, e.g.: sports armour energy (abbr: En) - Insulation against fire or cold damage, e.g. fire-fighter's suit piercing (abbr: Pr) - Tough protection, resilient to low energy sharp penetration, e.g.: chain links slashing (abbr: Sl) - Tough material resistent to cuts, e.g.: chain links Add 1/2 DR against damage of the listed protection types (minimum 1).

My proposal is to match these up with the existing armour in d20 games, and give a bonus to the DR against that type of attack.
The d20 modern game gives characters a defence bonus each level ("defense" in their US English).

I'll use that system (also presented as a variant rule in Unearthed Arcana) to let characters get better at not being hit as they get more experienced. With that in mind, I've lowered the defence bonuses granted by armour in the table below.

Armour________________Defence___DR____protection type
None
_______________________0_______0_______none
Padded
_______________________0_______1/-_____2/- vs Bl
Leather
_______________________0_______1/-_____2/- vs Sl
Studded leather
_______________________1_______1/-_____2/- vs Sl
Chain shirt
_______________________1_______2/-_____3/- vs Sl
Hide
_______________________1_______1/-_____2/- vs Bl
Scale mail
_______________________1_______2/-_____3/- vs Sl
Chainmail
_______________________2_______2/-_____3/- vs Sl
Breastplate
_______________________2_______2/-_____3/- vs Sl
Splint mail
_______________________2_______3/-_____4/- vs Sl
Banded mail
_______________________2_______3/-_____4/- vs Sl
Half-plate
_______________________3_______3/-_____4/- vs Sl
Full plate
_______________________3_______4/-_____6/- vs Sl
Leather jacket
_______________________0_______1/-_____2/- vs Sl
Light undercover shirt
_______________________0_______1/-_____2/- vs Ba
Pull-up pouch vest
_______________________0_______1/-_____2/- vs Ba
Undercover vest
_______________________1_______1/-_____2/- vs Ba
Concealable vest
_______________________1_______2/-_____3/- vs Ba
Light-duty vest
_______________________2_______2/-_____3/- vs Ba
Tactical vest
_______________________2_______3/-_____4/- vs Ba
Special response vest
_______________________3_______3/-_____4/- vs Ba + Bl
Forced entry unit
_______________________4_______4/-_____6/- vs Ba + Bl

[MeklorIlavator]

One problem with this method, at least in terms of DnD, is that DR doesn't scale well. Generally, by level 10, one can do 20 damage per attack before damage boosters/magic/maneuvers get involved. Having Damage Reduction 2 isn't going to help in this case. Plus, remember that each point of AC is a 5% greater chance of being missed, so the one for one DR trading isn't fair, either. This is alleviated somewhat by the Defense Variant you're using, though.


Additionally, looking at your system, your terminology is flawed. If Damage reduction can be beaten, then it should be listed by the types that beat it. Also, there's not such thing as energy damage reduction. What you're looking for is Energy Resistance, which has it's own rules.

[Godskook]

The scaling issues can be alleviated a little by adjusting the proficiency feats slightly to include the ability to wear multiple armors at once, something that is incredibly accurate historically. Padded Jacks and Chainmail would often be worn under plate. Give mettalic armors a hardness rating in addition to the DR, and give organic armors(leather and padded) a padding rating. Any armor with a hardness rating converts that much of incoming damage to bludgeoning, after applying DR. An armor's padding score is only good against bludgeoning.

So, to give an example of what I'm thinking:

Padded Jack
Weight: 5 lbs
Padding: 4
General DR: 0

Padded Jack +4
Weight: 4 lbs (20% weight reduction)
Padding: 8 (4 + 4)
General DR: 4 (0 + 4)

Chainmail
Weight: 35 lbs
Hardness: 3
General DR: 1

Breast Plate
Weight: 40lbs
Hardness: 8
General DR: 2

Breast Plate +2
Weight: 36lbs (10% weight reduction)
Hardness: 10 (2 + 2)
General DR: 4 (2 + 2)

So, a character wearing chainmail over a jack(both items above) suffers from a weight penalty of 40lbs, but has an effective DR 4/-.

Another character, wearing a breast plate +2 over jack +4, also suffers 40lbs of armor weight, but has an effective DR 16/-.

Wearing the jack +4 results in DR 4/- and 12/- vs. Bludgeoning.

Add other statistics as needed to get the flavor desired for each armor style.