I have been thinking about a gritty penetration-based, hit-point-less damage system for grittier RPG combat. The came to me when thinking about my Cepheus Atom rules, where you have "hit-point-equivalents" (Endurance and Lifeblood), but, in practice, you have wound levels based on these "hit points": Uninjured, Lightly Injured, Seriously Injured, and Dead. So, why should I use the wound levels directly, instead of going through the "hit points"?
Let's use Cepheus Light vehicle damage as an inspiration. Weapons have Penetration Dice. Ordinary handguns, knives, spears, etc. have 1d6. Rifles, light machine guns, big-ass pistols, long/bastard swords, etc. have 2d6. Sniper rifles, medium machine guns, grenade blasts, and broadswords have 3d6. Really heavy stuff such as RPG-7s and big lasers have 4d6.
Once you hit a target, you roll the penetration dice: 1-2 no damage; 3-5 light wound; 6-8 to severe wound; 9-11 mortally wound; or 12+ insta-kill.
Armor is a penalty to the penetration roll. Light armor is -3, heavy armor is -6, powered armor is -9.
A critical hit (let's say, a natural 12 on the 2d6 attack roll) adds one Penetration Die.
So, the probabilities of the various wound levels, once a hit is made, are (I hope I got the math right...):
Pistol vs. unarmored target:
33% flesh wound (no game effect)
50% light wound
17% serious wound
No mortal wound or insta-kill without crit.
Rifle vs. unarmored target:
8% flesh wound
33% light wound
42% serious wound
15% mortal wound
With light armor (-3 to the roll):
85% flesh wound
16% light wound
No serious+ wounds without crit.
27% flesh wound
56% light wound
15% serious wound
2% mortal wound
With heavy armor (-6 to the roll):
No damage unless on a crit.
73% flesh wound
25% light wound
2% serious wound
Now, let's factor in the to-hit chance: 8+ on 2d6 + attacker skill - target skill and assume equal skills, per shot fired:
71% miss or flesh wound (no game-relevant damage)
21% light wound
7% serious wound
61% miss or flesh wound (no game-relevant damage)
14% light wound
17% serious wound
6% mortal wound
With (common) light armor:
93% miss or flesh wound
7% light wound
69% miss or flesh wound
23% light wound
6% serious wound
1% mortal wound
What do you think of this system? Is it too lethal? Does it "feel" well in play?