Impaling, Piercing, and Beam Damage

Beam damage types

I will use the term beam damage to replace the Basic Set's tight beam burning damage type, simply because it is less cumbersome.

Size classes for piercing, impaling, and beam damage; size modifier; and wound multiplier

The wound multiplier for piercing, impaling, and beam damage comes from making a larger wound channel, but larger targets will suffer from a relatively smaller wound channel, and get the benifit of a lower wound multiple. Likewise, smaller targets suffer from larger wound multiples. Instead of using the bog standard GURPS piercing damage types and one impaling and beam damage type, I will rank piercing, beam, and impaling damage by size. To find the wound multiplier, subtract the victim's SM from the piercing size and look up the value on the table below:
Attack Size - SM
-8 -7 -6 -5 -4 -3 -2 -1 0 +1 +2 +3 +4 +5 +6
×0.1 ×0.15 ×0.2 ×0.3 ×0.5 ×0.7 ×1 ×1.5 ×2 ×3 ×5 ×7 ×10 ×15 ×20
pi & beam
×0.05 ×0.07 ×0.1 ×0.15 ×0.2 ×0.3 ×0.5 ×0.7 ×1 ×1.5 ×2 ×3 ×5 ×7 ×10
This follows the progression of the Speed/Range table: every +6 to attack size is ×10 to the wounding multiple. Every -6 to attack size is ×0.1 to the wounding multiple.

Note: The main reason for the SM dependance on wounding multiples is so that the blow through rule below gives reasonable results with the basic scaling relationship that HP is proportional to linear measurements.

Blow Through

High powered weapons are good at punching through lots of armor, but often just leave a small hole through their target. I want the rules for the damage caused by these weapons to have the following properties:

To realize these properties, the following modifications will be made. First, you only ever roll one die when determining damage. This die may be multiplied, added to, and so on as necessary to get the appropriate damage for the weapon. When damage for a weapon is listed as a number of dice (Nd+x), read this as multiplying one die by that number (1d×N+x).

Second, for man sized (SM 0) targets, basic damage delivered to the target by a piercing or beam attack is limited to 2 × the value rolled on the damage die after subtracting armor. For an impaling attack, this is limited to 1 × the value rolled on the damage die. Exception: The head and torso are protected by an additional 2 points of "armor." Unlike normal armor, these first 2 points of damage also cause damage to the person they protect. However, there is no additional wounding multiple for the brain or vitals hit location. This represents damage to the skull, vertebral column, ribs, or abdominal muscles that was stopped before it got to the brain, spinal cord, heart, or great vessels. It replaces the standard GURPS rules for DR 2 to the brain. This extra "armor" does not affect against attacks to the neck from the front or side, nor does it affect limbs or extremities.

This damage before blow-through is basic damage delivered, it is multiplied normally by the wounding modifier for larger and smaller piercing, beam, and impaling attacks.

Example: Bob is wearing a DR 15 ballistic vest and is hit by a 8d pi+1 attack from a big game rifle in the vitals. The first 15 points are absorbed by the vest, leaving 8d-15 to penetrate. However, bob can take no more than 2d+2 of this. If the damage roll is 3, the rifle delivers 3×8-15=9 points of damage through the vest, but Bob only sucks up 3×2+2=8 of that. The first 2 points have the usual ×1.5 wounding multiple for pi+1 but no multiple for the vitals (total 4). The next 2d have the ×1.5 wounding multiple for bullet size, times the ×3 wounding multiple for the vitals, for a total of ×4.5. Total injury to Bob is 2×1.5+6×4.5=30. Medic!

Critters or objects that are larger than man sized will take more damage if a weapon puts a hole all the way through them and have more muscle and bone to protect their internals; likewise smaller critters and things take less damage. The progression simply follows the Size and Speed/Range modifier table
SMBlow through damage cap (basic damage)Torso & Head protection
pi & beamimp
620d 10d7d
-11½d1d/2 + 12
-21d1d/3 + 11
-31d/2 + 1(1d + 1)/31
-41d/3 + 11d/31
-5(1d + 1)/31d/40

Special: If the damage before blow through result would round down to zero, keep track of fractional points of damage when multiplying by the wounding modifier and when determining wound severity.

Hit Locations

The wound multiples for the vitals and brain hit locations are applied after the wound multiples for weapon type, rather than replacing it. So a piercing attack (×2 for a SM 0 human) to the vitals (× 3) would do a total of basic damage × 6.

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