Penetration, Blow-through, and overly granular damage

My post on what guns do in GURPS and storytelling got me thinking about false precision in games that rate damage by HP ablation.

I’ll pick on GURPS, but DnD/Pathfinder is, in its way, not much different. Ironically, I don’t think people really notice as much in Pathfinder, since the entire point of an attack is to whittle away HP until the foe is Dead. Or Dying.

GURPS is a bit different, in that there are a few basically devastating outcomes (because of the one-second time scale) that don’t require HP ablation. You can KO someone with any blow to the skull, for example. Knockdown and stunning, both of which don’t necessarily require large HP subtractions. And lastly, criticals, and crippling of the limbs.

Anyway, here’s the thing. Let’s start with pistols. In common calibers, from about .380ACP to .45ACP (and maybe even including things like the .50 GI) are probably “equally ineffective” when it comes to doing their job. While the .380 is probably a bit anemic, and other cartridges like the 10mm Auto (720 J or so, 200 gr projectiles available? Ow.) are probably on the other end, there are no surefire manstoppers that achieve the goal due to size and power alone – everyone will tell you that shot placement (and a good bit of pscyhology, in addition to physiology) is at least as important, if not more, than joules, kg m/s, and caliber.

Don’t get me wrong – it’s likely, perhaps certainly – true that on the margin, higher energy and momentum and caliber are more likely to achieve incapacitation. But until you up the ante to things like a .44 Magnum (in a pistol caliber), or a .223 or similar high-powered cartridge, you’re really saying that in certain edge cases, you’re slightly more likely to get’r’done than you were before.

What I’m about to do is clearly the act of pondering doing away with Hit Points and going to a wounding mechanism based on something like a HT roll, probably penalized. Probably something like “every HP/2 of penetrating injury is -1 to a HT roll; the more by which you fail, the worse off you are.”

I’m not going to work this one out in detail. Just suffice to say: despite my endless fiddling with firearms game mechanics that are super-detailed in resolution, the world doesn’t really work that way when people are involved; even armor plate is frustratingly variable under real-world conditions.

23 thoughts on “Penetration, Blow-through, and overly granular damage

  1. "there are no surefire manstoppers that achieve the goal due to size and power alone"

    You should stick to the analysis of swords and leave ballistic analysis to this who know a little more about it. The .40/10 mm and the .45 are without a doubt manstopper and I would take one against any opponent any time. They are design for one purpose and only one, to stop a man in their tracks and have proven over a hundred years in military and civilian service to do just that, stop men.

    1. Hee. You should follow the link I have to my very, very detailed analysis of penetration and wounding here:

      Please suffice to say that I have more than a little knowledge of ballistics, interior, exterior, and terminal. When I say "no surefire manstoppers," I mean that just hitting with a 10mm or .45auto is not sufficient. You have to hit the right spot. Hell, people get hit with .223 (as in the Black Hawk Down incident) and don't go down always, of a necessity, boom, you're stopped.

      I've got a .40 S&W and a .45ACP myself – and I chose them because they're nice, popular calibers and I do believe that higher cross section is better at pistol-level. But let's face it: these are defensive weapons of last resort, and the differences in caliber are more-or-less marginal once you get into the "somewhat serious" caliber and energy levels. Some put this line at .380ACP, I'd tend to put it at 9mm, and I prefer the .40 and .45 – my hands are a bit too small for the 10mm, but it's no question a great pistol cartridge.

      Even beside that, I'm talking about GURPS, which applies points of damage in a fairly deterministic way, and where the law of averages means that when you're looking at penetration/injury, things aren't nearly as random as they are in real life.

  2. Do you really believe that a single shot of .45 ACP, fired randomly and off the centerline of the torso, is sufficient under all conditions to stop a man? If so, do you have statistically significant data to back that up?

    If not, stop posturing and contribute to the discussion.

    Doug, I started writing a wounding system for GURPS here: It's a good place to start but I don't know how well it would work in play.

    1. Thanks for the link, Mark – and the conditions you mentioned, single shot and off-centerline, are exactly the kind of thing I was talking about when I was talking about surefire manstoppers if you purposefully neglect psychology and shot placement – which is to say, ignore nearly everything.

      I'll read your link today!

    2. Of course, the only projectiles that are liable to meet these criteria are 20mm or larger, but that's the point.

      I'd be quite interested in a robust system that was both playable and provided some of the variability inherent in throwing tiny bits of metal really fast to hurt people.

    3. Mark: The only place I'd consider going (though I'd need to test it) from where you started is to look at some sort of HT roll to alter the wound category, potentially. This is largely due to the stochastic nature of the damage, since for some attacks it's nearly impossible to roll a graze (you can't get grazed on the arm for 1 point with a 3d attack unless you've got armor).

      The other thing I might do for all wounds is a Fight Check, even for a graze. Tactical Shooting suggests a check for being (nearly) MISSED by a bullet, after all. 🙂

  3. I'm always leery of qualitative rather than quantitative systems, but I'm also beginning to balk at the strict reliance on the d6 in GURPS.

    This reliance (and I'm picking on GURPS, but it is present in most games) adds a mechanical limitation on lower-bounds on high-damage attacks, which really becomes apparent when you're dealing with firearms and more powerful attacks (e.g. A shot from a 7.62mm round does a minimum of 7 points of damage). I'm at a loss for how to deal with it, short of replacing every d6 after the first with 1d-1, and figure out a way to convert all static bonuses into dice.

    1. Grazes- Any hit by zero or defense failed by 1 results in a half damage hit. Both at the same time is a quarter damage hit. Optionally also double DR, quadruple for both at the same time.


    2. Yeah, that's what I've had to settle on, but it still feels clunky. And it works fine up to the AK level, but if you get into anything higher, Ultra-Tech levels for example, it starts to break down again.

      But then again, maybe a Rainbow Strike Laser should do a minimum of 7 damage on a minor graze…

  4. I'm experimenting by halving firearm damage and giving it a (2) armor divisor in my two FTF games. It has definitely made shot placement much more critical to dropping people with pistols, to my players' annoyance (though I expect they'll be less whiney once someone shoots them a couple times). Especially coupled with graze and near-miss rules, I feel this does a pretty good job of having firearms be something that you can take minor hits from, but if you get hit somewhere vital will still ruin your day and does a decent job of punching through armor.


    1. I know David Pulver likes that solution, and it seems to give some pretty sensible results. If one is pretty rigorous about post-fight bleeding and medical care, this could work pretty well.

  5. You know the comment you made here:

    "Probably something like "every HP/2 of penetrating injury is -1 to a HT roll; the more by which you fail, the worse off you are."

    Makes me laugh a tad bit. This same exact system is something that True20 and Mutants and Masterminds is well known for, though instead of dealing with straight Hit Points and Damage Reduction, the Player has instead a Toughness Score and Impervious Toughness (which can, to some degree, emulate this).

    Though where it differs is that GURPS uses both Strength and Health to determine the result of damage. In Mutants and Masterminds the player has a straight Toughness Stat, and by dealing enough damage to bypass that stat the more likely that player is to succumb to more lethal affects, though with a hard enough hit they can be completely KOed outright.

    With how detailed the system is, I haven't bothered to try to convert GURPS to a similar system, as I do understand that Strength is pretty centric to the system as it is, and eliminating the need for HP and putting more emphasis on Health rolls would be fairly game altering.

    I am very curious to see what further analysis you have to share, even considering how foreign some of these terms are (Mostly due to the fact that I have an overwhelming fear of the subject matter).

  6. The problem I have with Wound Threshold systems has always been that you end up with the lucky being able to shrug off truly ludicrous amounts of low damage attacks. IIRC Savage Worlds uses something similar, and IME there are a lot of complaints about hits that connect but don't do anything because the target makes his Toughness/whatever check.

    Perhaps some sort of cumulative penalty based on how many resistance rolls you've had to make recently or something. Hrm…

    1. What I'd try and do is ensure that you can only mitigate a wound so far. You might also have minor penalties stack, so that the shock penalties for minor wounds last more than 1 sec, and several -1 penalties add up.

      But at the core, you're right: getting filled full of lead should be bad for you. 🙂

    2. Well, for a pretty realistic hard-hitting game, that makes total sense. Though in a Comic Book/Manga type setting where this kind of thing happens fairly regularly, it works out pretty well.

      Not to mention, those who typically DO get hit on a regular basis tend to have a higher toughness to take larger hits. Very rarely have I had an "average" or "below average" character who actually got hit survive those larger attacks.

      The thing that I am not quite unsure of, is isn't the Shock Penalties and rolls for death fairly significant as is? Only time I have seen people handle attacks like this is if they were fit/very fit to help cushion their Hit Point Pool. In general, an "average" person typically would not be able to handle many of these attacks, as if I am not mistaken in a system like GURPS, there are damage multipliers, and fairly significantly so for piercing.

      Why would a penalty, in additional to shock penalties, even be necessary? In games I have played where I wielded a great maul, bludgeoning damage was pretty significant with flat damage, especially with Trama damage to boot. Add in penetrating and piercing damage? It can be pretty lethal, and have a lot of stopping power behind it due to significant shock penalties.

    3. The HT penalty is there to prevent the HT 12 to HT 14 "get out of jail free" card that can happen. While you can suffer a KO roll at 0 HP and start making death rolls at -1xHP, with high HT I've heard tell that it's basically "keep going until you absorb 6xHP damage and die."

      This may well be a bit of an exaggeration, and any new wounding system would require active playtest. But If you took a -1 to a HT roll for every HP/2, then even a HT 14 person who ate a big blow might be at only 50% success with a -4 penalty (possibly STILL too high!) instead of the 90% that is a straight roll vs. HT.

  7. Geez. Do I dare post again? I'll make two statements.

    1. The .45 ACP was designed as a manstopper for the Army and has done its job. They went away from it in the interests of commonality with NATO and are starting to go back to it. View the recent order by te USMC for 25,000.
    2. I used to trust my life to .45 ACP in a Glock 21 every day.

    I'll say no more.

    1. Regardless of whether we see exactly eye-to-eye on this particular issue, I wanted to thank you for commenting on my blog. Debate is healthy, especially if conducted with decorum.

      I also note from your profile that you are a veteran, so I want to thank you for both your service and sacrifice.

      I hope you will continue reading, and I look forward to further comment. You can be sure that firearms are a topic that will recur frequently on this blog!

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