House Rule for Realistic Armor Penetration

[phayman53]

In this thread I mentioned a house rule that I have play with that seems to work pretty well for fixing the problem of muscled powered weapons penetrating armor too easily (which I believe is too high even at normal ST ranges and with most damage types, not just cuts). The design of this rule was based on a few premises. The first was that I wanted something that better approximated, in my understanding, the performance of various types of weapons against realistic armor. The second was that I wanted to change as little of RAW as possible, especially not wanting to rescale ST damage progressions. The third was that I wanted to make it as simple to implement as possible, requiring no or very few additional calculations during play. This rule is meant to replace the "Blunt Trauma and Edged Weapons" rule on pg 102 of LT, so it is not designed to work with it. Please let me know what you think!

House Rule for Realistic Armor Penetration with Muscle Powered Weapons:

Realistically it is very hard to cut or pierce armor with muscle powered weapons, much harder than the GURPS standard rules make it. Here is a revised rule:

1) All muscle powered weapons receive an armor divisor based on their damage type and weight distribution:

Balanced Cutting Weapons: (1/3)
Unbalanced* Cutting Weapons: (1/2)
Impaling Weapons: (½)^
Balanced Crushing Weapons: (½)
Unbalanced* Crushing Weapons: (1)
Piercing weapons and all other damage types: (1)
EDIT: All weapons that already have an AD have there AD halved, subject to GM customization.

*Unbalanced is any weapon that has a U in its parry statistic, all others (including unarmed attacks) are balanced.

^For added realism, some swords (Many spathas, Viking, and Oakeshott type X, XI, and XIII swords for example) and other kinds of weapons should have a thrust imp AD of (1/3)--basically, any weapon that does imp damage but does not have a very acute and stiff point. They tend not to thrust through resistive materials well at all. However, this may be too much realism for some people.

2) All Two-Handed weapons get an additional +1 to their damage values to represent the greater usefulness of these weapons against armor.

3) Even though armor was extremely protective against edges and points, blunt trauma could still get through it--especially flexible armor. The standard Blunt Trauma and Flexible Armor rule is replaced with the following:

Blunt Trauma Through Flexible Armor:
All Unbalanced Weapons do 1 point of injury per 3 points of damage stopped by flexible DR. This injury is never multiplied for damage type or hit location, but is added to any injury inflicted by damage in excess of DR.

All Balanced Weapons do 1 point of injury per 6 points of damage stopped by flexible DR. This injury is never multiplied for damage type or hit location, but is added to any injury inflicted by damage in excess of DR.

Blunt Trauma Through Rigid Armor:
All Unbalanced Weapons do 1 point of injury per 6 points of damage stopped by rigid DR. This injury is never multiplied for damage type or hit location, but is added to any injury inflicted by damage in excess of DR.

All Balanced Weapons do 1 point of injury per 12 points of damage stopped by rigid DR. This injury is never multiplied for damage type or hit location, but is added to any injury inflicted by damage in excess of DR.

Blunt Trauma through a Combination of Rigid and Flexible Armor:
The presence of rigid armor effectively makes all DR rigid. Use the rules for blunt trauma against rigid armor.

Example: Sir William the ST15 Knight swings his Thrusting Broadsword (2d+2(1/3) cut) at Sir Jean, who is wearing a fine mail Hauberk (DR4/2*cr). The effective DR of the Hauberk against this blow is 12. If Sir William rolls average damage he will do 9 damage. That means the Hauberk stopped his blow. However, his blow was powerful enough to injure Jean through the armor, doing 1 point of bludgeoning injury. If William rolls max damage he will do 14 cutting damage, which means he will defeat the DR by 2 cutting damage and deal 3 injury from the cut plus 2 bludgeoning injury, totaling 5 injury. If Sir William chooses to thrust instead he does 1d+3(1/2)imp damage, averaging to 6.5 damage. Not enough to penetrate the Hauberk’s effective DR of 8, but enough to do 1 point of bludgeoning injury. However, a max roll would do 9 damage, defeating the DR by 1 imp damage, resulting in 2 injury from imp and 1 from bludgeoning, 3 total. Such a thrust to the vitals would result in 4 injury instead. In all cases, the Hauberk prevented a major wound from a one hand blow from an exceptionally strong warrior.

However, if Sir William were using a mace, his damage would be 2d+4 cr, averaging 11 cr damage. This means that an average hit through Sir Jean's mail would do 9 damage, almost always a major wound! Furthermore, a max damage hit would do 14 cr damage, enough to put most warriors into negative HP.

Optional, Untested Situational Rules:

1) Armor that is braced against a rigid surface is significantly easier to penetrate. The Armor Divisors of every kind of attack is multiplied by 2 if the target is pressed against a rigid surface. This means that a balanced cutting attack would go from an AD of (1/3) to (2/3). Situations where this applies are:

1) Any time the target is prone or supine.
2) Any time the target is pressed against a sturdy wall.
3) Any other time the GM rules the target would not be able to give at all with a blow.

2) The head is vulnerable to trauma caused by sudden head movement caused by a blow, even if armor otherwise protects the head from all other damage. Any damage to a head hit location in excess of 50% of the DR on that location does 1 point of injury. This injury is not multiplied for hit location, but it does cause appropriate rolls against knockdown and stunning.