v2.0

(07.03.27: I'm dropping the "draft" disclaimer; it's a real article now.)

My old GURPS Diner article Gird yer Loins! contained two simple ideas for better handling body armor in GURPS: dropping the troublesome PD stat, and introducing a new Edge Protection (EP) stat.

PD has indeed departed from GURPS 4e, so the first idea's text can be retired for good.

The second idea is not any official part of GURPS, yet it (or some variant) is used by many gamers and pops up frequently in online discussions of armor. I'm moving that part of the old article into its own new article here on the Games Diner. In the future, it may get folded into a larger treatise on armor; for now, here's the simple idea on its lonesome.

The current rule

GURPS handles flexible armors like mail as follows: the wearer suffers one point of "blunt trauma" damage per full 10 points of damage (5 points if crushing) that doesn't penetrate DR. In addition, some of these armors have a split DR score that offers full protection vs cutting and piercing damage, and reduced protection vs crushing and impaling damage. (See BS 379, and armor tables on BS 282-6.)

That makes for a workable but quite limited model. Flexibility becomes a simple binary switch (though the flexible armors with split DR could be seen as a third "very flexible" configuration). It doesn't offer a good way to model armor like Frodo's thin but unbreakable mithril shirt, which, as painfully demonstrated in The Fellowship of the Ring, will completely stop an edge from penetrating yet will let a huge wallop whack the wearer. But if DR is less than 10 (or 5 vs crushing), the GURPS "blunt trauma" effect can't come into play anyway, making the "flexible" designation meaningless for almost all low-tech armors.

Oddities pop up, too. Even when DR is substantial enough to allow for the "blunt trauma" effect, a damage roll that goes just a little over DR and penetrates the armor can inflict less injury than a roll that's fully blocked by flexible DR. On the lower end of the DR scale, armor with the split DR characteristic can infamously let an attacker deal more damage to the wearer by striking with the flat of his edged weapon, using this makeshift club to force the armor's lower DR vs crushing.

There's no huge problem with all of the above; it plays fine if you don't look for the bugs. But for the interested, below is an alternative way to handle blunt trauma from armor deformation. It's more realistic and flexible in what it models and avoids the above oddities, yet is easy and GURPS-like as well.

Edge Protection score

In addition to DR that completely negates the impact of a blow, armor can offer a lesser form of protection that allows the impact of a blow through, but prevents its edge or point from penetrating the armor (and thus flesh). I measure this property in points like DR, and call it Edge Protection (EP).

Subtract DR normally from basic hits. These hits are absorbed by armor. From there, apply three simple rules for EP:

1) If the weapon is crushing, there's no additional protection from EP. We're done.

2) If the weapon is edged (cutting, impaling, or piercing), basic hits left over after DR, and up to EP, deal crushing damage. The weapon deforms the armor and hurts the wearer, but EP doesn't let the edge through.

3) Basic hits from an edged weapon that exceed DR + EP do penetrate the armor. Those basic hits affect flesh in their usual manner.

These rules replace GURPS 3e's "roll of 5 or 6" rule, or 4e's rules for flexible armor and blunt trauma. There's no special "flexible armor" designation under these rules; the combination of DR and EP models an armor's unique resistance to both deformation and penetration.

Example: You're wearing chain mail with cloth underneath, for DR 2, EP 5. You're attacked with an axe.

Your DR absorbs a blow of 2 or less damage. You're not hurt.

A 4-point blow, after DR, leaves 2 basic hits. But those hits don't penetrate EP 5; the mail is not cut. You take 2 points of crushing damage.

A 13-point blow, after DR, leaves 11 basic hits. EP limits the next 5 points to crushing damage; the mail isn't cut yet. But the remaining 6 points break through the mail and cut you normally, for 9 damage after the cutting multiplier. You take 5 crushing + 9 cutting = total 14 points of damage.

If the weapon were a club instead of an axe, you'd just subtract 2 from damage for DR, and be done with it. EP would offer no special protection.

Normal armor divisors affect both DR and EP equally.

Benefits of EP

The benefit of EP to the armor wearer is obvious: edges hurt! A claymore swat to your mail-covered midsection may still knock the wind out of you, but that's a heck of a lot better than getting chopped into haggis. The effect is particularly important where sensitive parts are concerned, most notably impaling and piercing attacks to the vitals. A little EP there can save you a lot of injury!

EP's clear distinction between armor penetration and non-penetration can be useful to GMs, such as in determining whether a venomed weapon delivers its poison, or in implementing rules for accumulated armor damage and deterioration.

EP nicely simulates the ability of armor – even low-tech armor with modest DR – to keep its wearer in possession of his limbs, yet still get rudely battered by those axes and swords. And as shown below, EP allows for much greater customization of armor than DR alone does – up to and including magical armor that's "impenetrable", yet leaves the wearer anything but invulnerable.

Cost of natural EP

EP protects less than full DR. As natural armor, treat EP as a -60% limitation on the cost of DR, which becomes 2 cp per point of EP.

Setting armor DR and EP

DR represents resistance to any deformity at all; EP represents resistance to penetration but not deformity. The more flexible the armor, the more its protection will take the form of EP instead of DR. Tough, hard material, like a bronze chest plate, has high DR and low EP. Tough, flexible material, like mail armor, has low DR and high EP.

To rework existing stats, below are rules of thumb. Round values to the nearest integer (rounding up on 0.5). Keep in mind that a point of EP offers less protection than a point of full DR; reworked armor's total DR+EP should at least equal listed GURPS DR, to maintain overall level of protection.

However, any armor can vary considerably from the suggestions below, especially in EP.

Very flexible armors: These would be the BS p283-4 armors given a "flexible" asterisk and a split DR score (higher score vs piercing and cutting, lower score vs others).

Set DR vs all attacks to the lower DR score. Then set EP equal to the higher DR plus half the lower – but halve EP vs impaling.

Example: Mail has DR 4/2. Use DR 2 vs all attacks, plus EP 5 (but EP 3 vs impaling).

Semi-flexible armors: These are armors with the "flexible" asterisk and a single DR score, like cloth and light leather.

Set DR to listed DR minus a quarter. Set EP equal to listed DR.

Rigid armors: These are armors without the "flexible" asterisk, like scale and plate.

Set DR to listed DR minus a fifth. Set EP to a third of listed DR.

Extreme cases

An Impenetrable Coat of Armor bequeathed by the gods might have no more DR than normal armor, but infinite EP. You can be bludgeoned to death wearing it – fairly easily so if it's flexible with low DR – but it won't be penetrated.

Make that a thin Shirt of Impenetrable Mono-silk, and you can have zero-DR armor that's of no value in a fist fight, yet will stop a sword from running you through.

On the other end of things, a theoretical very hard, strong, but brittle armor, perhaps ceramic, would have high DR and no EP. Damage above DR simply breaks through the armor.

Sample Armor Table

Below are standard GURPS armor types, reworked with new DR and EP stats following the rules of thumb above.

armor	GURPS DR	New DR	EP	notes
Cloth	1*	1	1	-
Leather	2	2	1	-
Lorica Segmentata	5	4	2	-
Mail	4/2*	2	5	DR 2, EP 3 vs impaling
Double Mail	5/3*	3	7	DR 3, EP 4 vs impaling
Scale	4	3	1	-
Steel Corselet	6	5	2	-
Heavy Steel Corselet	7	6	2	-
Frag Vest	5/2*	2	6	DR 2, EP 3 vs impaling
Tactical Vest	12/5*	5	15	DR 5, EP 8 vs impaling
Tactical Suit	20/10*	10	25	DR 10, EP 13 vs impaling
Impenetrable Magic Armor	(hypothetical)	?	infinite?	DR depends on rigidity. EP limited only by definition of "impenetrable".
Dwarven Magic Mail	(hypothetical)	4	12	DR 4, EP 6 vs impaling
Dwarven Magic Plate	(hypothetical)	8	10	DR 8, EP 5 vs impaling

 

Tweak those numbers as you like. Scale armor, for example, happens to get the worse of rounding on both DR and EP; boosting one of those by a point might be fair.

Also, it's uncertain how plate inserts for modern flexible armor should be handled. The added plates presumably make the armor anything but flexible where impact is concerned; perhaps it's best to add the plate DR to the lower of the original split DR score, and call that a single overall, non-flexible DR score with no EP.

Variations and tweaks

The above covers everything you need to play with EP. Below are options for the interested.

EP and attack types

EP can vary with attack type. The guidelines above already suggest halving EP vs impaling damage, for those flexible armors that GURPS designates as especially vulnerable to impaling. You may think of other worthy tweaks. As an extreme example, your Impenetrable Magic Armor's infinite EP may drop to a low value (even zero!) when faced with the All-Penetrating Magic Sword.

Likewise, detail-oriented GMs will find EP a good way to model weapon sharpness. A blunt edge might double EP, and a very sharp edge halve it. This nicely modifies weapons' armor-piercing ability without mucking up overall base damage or overplaying the role of DR.

EP and bullets

EP is definitely useful against large and huge piercing attacks, protecting the target from these weapons' damage bonuses. EP will also save you from extra hurt vs small and regular piercing attacks to the vitals.

But EP leaves you no better off when regular piercing attacks hit non-vital targets – and it'll actually hurt you more when small piercing attacks strike non-vitals! (EP turns those hits into regular crushing damage for a x1 multiplier, replacing the usual x0.5 multiplier for small piercing attacks.)

That's not a flaw in the EP rules. GURPS rules that, compared to a blunt attack of a given force, a flesh-penetrating attack of the same force (i.e., same basic hits) can inflict the same damage (as with regular piercing) or even less damage (as with small piercing) than the non-penetrating equivalent. Whether this reasoning rings true or not, the above EP "oddity" is only following it to the letter.

It's up to you whether that's just as things should be, or a problem to be addressed. If the latter, you could rule that EP offers the lower of a crushing damage multiplier (x1) or the attack's innate multiplier (x0.5 for small piercing vs non-vitals). If nothing else, that keeps EP from making the wearer worse off when small calibers attack.

Simplified EP

Using EP requires little extra work. But if you dislike even that, here's a simpler version:

Subtract DR from basic hits, as always.

If remaining damage is less than or equal to EP, then damage is crushing (per rules above).

But if remaining damage exceeds EP, treat all of it as penetrating, with its normal damage multiplier; don't bother adding the EP-blocked crushing damage to the EP-penetrating edged damage.

Example: You have mail with DR 2, EP 5.

DR absorbs an axe blow of 2 or less damage; you're not hurt.

A 4-point blow, after DR, leaves 2 points of crushing damage, which doesn't penetrate EP 5; the mail is not cut.

A 13-point blow, after DR, leaves 11 basic hits. Those 11 points exceed EP; the mail is penetrated and EP offers no protection. Treat as a normal 11-point cutting attack, inflicting 16 damage after the x1.5 multiplier.

Complexified EP

Want the ultimate in armor realism? Use the full EP rules, with one addition:

For any and all impact absorbed by DR, apply 1/5 (round down) as blunt trauma damage.

That's for any armor, flexible or rigid or in-between. When armor "absorbs" a hit, it's only spreading it out over a large area. A great big wallop, even spread over a large area, will still hurt!

Example: You wear a heavy steel corselet with DR 6 (and EP 2, though that's not relevant to this example).

Any time you're hit for 5 or more damage, from any impact, apply all DR and EP rules normally... but when you're finished, add one more point of blunt trauma, for the initial impact of the corselet slamming hard against you.

Final variant

With that said and done, there's yet one more variation possible: use both the above simplified and complexified rules. Yes, they work together fine, resulting in something similar to the default EP rules in complexity, just a bit different in results.

EP and GULLIVER Toughness

How about GULLIVER's redefined Toughness? This isn't 3e's Toughness; it's protection (generally from muscular or otherwise stout flesh) that lessens crushing blows a lot, slashes less so, or a stab to the vitals very little; it's in some ways the opposite of EP. (Game terms: Toughness only subtracts from the basic hits of an impact, not the additional damage from edges, penetration and hit location.) Sounds like it'd be hard to juggle DR, EP, and this new Toughness, no?

Turns out it's really very simple: Toughness and EP combine to form DR. A point of EP turns a point of edged damage into crushing, and a point of Toughness absorbs that point of crushing damage.

Example: You have Toughness 3, and put on DR 2, EP 4 armor. Toughness and EP combine to become DR 3 with EP 1 left over. Treat the total as DR 5, EP 1.

If you instead wear DR 1, EP 1 armor, Toughness and EP combine to become DR 1 with Toughness 2 left over. Add this DR to the armor's DR: net DR 2, Toughness 2.

Let Toughness be a -40% limitation on the cost of DR, which makes it 3 cp per point. A point of Toughness and a point of EP add up to a point of DR in both cost and effect.

Toughness is very optional, and is a tangent to this article; I mention it here only for anyone with an interest of using that and EP together. In practice, DR and EP alone are probably as much detail as many players will want. I'll note in closing, though, that with EP to stop edges from penetrating, Toughness to model absorption of blunt force, and DR to combine the effects of both, you can model just about any armor effect with great realism.

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