Base gun damage on calibre and gun size; armor divisor on kinetic energy?

[Tomsdad]

Originally Posted by Varyon

Of course, what we're discussing is, in fact, a CNS wound - a .45 ACP to the brain (via Skull). I don't know exactly how quickly and reliably that tends to make someone dead, but I'd imagine survival - even with immediate intervention - is rather the exception. Going with an average 20 HP Injury, if I'm remembering the way bleeding (and bleeding from Skull hits) function, that's a 50% chance to initially survive (and ~34% chance of "only" being mortally wounded, with instant death happening ~16% of the time), then an HT-4 roll (-1 per 5 HP lost) every 30 seconds to avoid bleeding. Rolling a 5 or 6 three times in a row is pretty unlikely, so natural recovery likely only happens with a Critical Success (3 or 4). With a 1.85% chance to stop bleeding each check, a 7.39% chance to avoid losing HP but continue bleeding, an 86.12% chance to lose 1 HP, and a 4.62% chance to lose 3 HP (Critical Failure on 16+), you're looking at an average loss of 1 (0.9998) HP every 30 seconds. You have a ~15% chance to stabilize before the next death check threshold, ~30% by the threshold after that, ~42% by the threshold after that, and ~52% just before reaching -5xHP. Overall, the chance to survive an average damage .45 ACP to the Skull isn't great without intervention, but isn't atrocious either. 16% die outright, 34% suffer mortal wounds, and 50% survive without qualifiers. Of the latter 84%, 15% (12.6%) stabilize on their own before hitting the next threshold. Of the 71.4% remaining, 50% (35.7%) keep going, 17%* (12.14%) suffer mortal wounds, and 33% die (either from failing by 3+ or failing at all when already mortally wounded) at 300 seconds (5 minutes). Of the remaining 47.84%, 15% (7.18%) stabilize on their own before hitting the next threshold. Of the 40.66% remaining, again 50% (20.33%) keep going, 17%* (6.91%) suffer mortal wounds, and 33% die at 600 seconds (10 minutes). Again, 15% (4.086%) stabilize, and of those remaining 50% (11.58%) keep going, 17%* (3.94%) are mortally wounded, and 33% die at 900 seconds (15 minutes). For our last iteration, 15% (2.33%) stabilize, the rest die at 1200 seconds (20 minutes). So, in total, around 26% stabilize on their own. Of those 26%, quite a few are mortally wounded, although I feel working out the probability for that is a bit more time-consuming than I'd like to bother with, but probably less than 50% (13% total), the bulk of which will die from the mortal wounds in several hours without intervention.

TL;DR: So, of those who get an average damage .45 ACP to the noggin and receive no medical attention, ~15% will survive, ~16% will die outright, ~23.8% will die in 5 minutes, ~13.5% will die in 10 minutes, ~7.7% will die in 15 minutes, ~11.1% will die in 20 minutes, and the rest - ~12.9% - will die over the course of hours due to being mortally wounded. Different damage results will shift these around in expected ways (high damage means more die, low damage means fewer die), but this probably isn't terrible to use for the average. Those who get medical attention will fare better, although the clock is certainly ticking (and brain surgery isn't exactly easy). I don't know how close this comes to reality, but I suspect it's rather on the lenient side.

*I'm pretty certain I messed up a bit on the math to calculate the proportion that hit their first mortal wound at each step beyond the first, but I really don't feel like going back and recalculating all of that. Just keep in mind those numbers are probably close but not quite right and you should be fine.

On the direct damage on the CNS vs. death by rapid bleeding out you could distinguish this further in game than the system currently does.


So the locations we're discussing lead to death in one of two ways:

1). having some high injury multiplier and no upper injury cap leading to big instant HP loss

2). having worse than normal bleeding rules. Some combination of bleeding faster (30 sec per roll not 60 sec), being harder to stop (a negative mod to do so) or requiring surgery not just first aid to directly stop bleeding. Surgery having it's own set of situational mods as well.

But some things stay the same for example make three successful bleeding rolls in a row (or get one critical success) and you stop bleeding.



In terms of the realism debate the "downside" of the first is that in terms of killing you it's all or nothing, i.e. it either leads to a unsuccessful death roll, or it doesn't.

The downside of the second is that it can be seen to take too long (you are losing 1 or 3 hp per failed roll on 30 second schedule) but barring good intervention bleeding at penalty from HT10 is bad news even if it's not super quick. (IME this where the distinction between first aid and surgery becomes v/important).

so really the current bleeding rules do that job it's just they might not be fast enough to be super realistic. As per Douglas Cole's post. Of course since in general the 2nd follows the 1st they combine here!

NB: I'm not sure how that link matches up with your figures, a 10HP/10HT target getting hitting through the skull for 5 points of damage leading to a 20 point injury will bleed at -4 or equivalent HT6 and an average loss of 52.9 hp before stabilising. i.e. an average total of 73 hp lost so hitting the -5xHP threshold becomes a more relevant limiting factor here than how much you bleed on average (but I also get you are approaching this in a different way by assessing the probability of range of outcomes).


A simple solution here might be just to further reduce down the cycle of bleeding tests for some wounds/locations we think should bleed quicker than 1hp/3hp per 30 seconds.

But as I said earlier there is a risk that we just end up with a different way of describing "and they're dead" without adding too much to our games but rolling a lot dice and fishing for crits.

[Varyon]

You could in theory expand out the rules for mortal wounds, so there's somewhere between "dies instantly" and "probably bleeds out in 5+ minutes." Say, failure by 1 means normal mortal wounds rules, failure by 2 means the character has mortal wounds and will die in 1d hours unless they are stabilized, failure by 3 means death in 1d minutes, failure by 4 means death in 1d seconds (likely requiring magic or superscience to avoid), and failure by 5 means actual instant death. Alternatively, outside of failure by 5, have the character make another death check when time elapses; critical success upgrades you to just suffering mortal wounds (or maybe just upgrades you one step, from seconds to minutes), success restarts the clock, failure downgrades you by MoF steps (1d hours->1d minutes->1d seconds->death).

[DouglasCole]

Originally Posted by Varyon

I don't know how close this comes to reality, but I suspect it's rather on the lenient side.

As noted above, final biological activity for President Kennedy was 22 minutes after being shot in the head with a rifle. From a game perspective, he died immediately.

A recent study focusing on the Survival of Penetrating Injury to the Brain (SPIN rather than SPIB, for cool-acronym reasons) assessment, found a 42% survival rate of those admitted to trauma centers for penetrating wounds to the brain, most of which were gunshots. Self-inflicted and military wounds have skewed the results in the past was one of the notes.

Big thing in the above is surviving to get to a Level 1 Trauma Center. If you die on the street from a brain injury, they don't take you there; they take you elsewhere.

[Tomsdad]

Originally Posted by Varyon

You could in theory expand out the rules for mortal wounds, so there's somewhere between "dies instantly" and "probably bleeds out in 5+ minutes." Say, failure by 1 means normal mortal wounds rules, failure by 2 means the character has mortal wounds and will die in 1d hours unless they are stabilized, failure by 3 means death in 1d minutes, failure by 4 means death in 1d seconds (likely requiring magic or superscience to avoid), and failure by 5 means actual instant death. Alternatively, outside of failure by 5, have the character make another death check when time elapses; critical success upgrades you to just suffering mortal wounds (or maybe just upgrades you one step, from seconds to minutes), success restarts the clock, failure downgrades you by MoF steps (1d hours->1d minutes->1d seconds->death).

Yep, that's another way to go although if the concern is people aren't bleeding out and dying quickly enough in RAW you might want to set the death roll at say -2 or even -3. Otherwise on a straight HT roll you have lot of people at those stages who'd otherwise just be dead by RAW.

It would also only kick in once you've lost enough HP to qualify for a death roll.

[Fred Brackin]

[QUOTE=DouglasCole;2358425t, found a 42% survival rate of those admitted to trauma centers for penetrating wounds to the brain, most of which were gunshots. Self-inflicted and military wounds have skewed the results in the past was one of the notes.

[/QUOTE]

Was there some sort of filter used?

It'd be eaasy to exclude the military results (which involve higher energy rounds more often) but including self-inflicted wounds would skew because of the people who put the gun to their temples (which can cause blindness and lobotomy but misses the brain stem).

[DouglasCole]

Originally Posted by Fred Brackin

Was there some sort of filter used?

It'd be eaasy to exclude the military results (which involve higher energy rounds more often) but including self-inflicted wounds would skew because of the people who put the gun to their temples (which can cause blindness and lobotomy but misses the brain stem).

I was reading a summary of the summary in the news media. My intepretation of the quote was that they were comparing conventional wisdom about brain injury with the reality of survival rate (about 40%; 20% of wounds were self-inflicted) at some of the best equipped and staffed trauma centers.

My impression was a systematic look at such injuries hadn't been done recently. Some of this could be synthesized surprise as they were trying to promote their SPIN-score methodology.

Anyway, the data above is - as I noted - a selected subset. Folks have to not die on site, and the study noted that those transferred to Tier 1 trauma centers did much better than those less-equipped to handle such injuries.

Anyway, I feel like I'm digressing. The stats Varyon showed for mortality from a .45 gunshot wound seem close enough for me. "One shot KO" is really the key bit for no longer being a threat from a game perspective; the rest is mostly window dressing for foes, or important after the battle for PCs and prime NPCs, who often will survive or not based more on "how much the GM cares" than lots of die rolls.

[Varyon]

Originally Posted by DouglasCole

Big thing in the above is surviving to get to a Level 1 Trauma Center. If you die on the street from a brain injury, they don't take you there; they take you elsewhere.

Yeah, that's going to skew things toward what in GURPS looks like the lower-damage results. In my average-damage calculations, unless the target goes from "shot in the head" to "on the table with a trauma team working" in rather short order, a large proportion of those who make it to the table are going to have stabilized their bleeding on their own, with medical intervention only necessary to stabilize mortal wounds and perhaps avoid the Lasting Wounds results from Martial Arts. Someone who gets hit for 4, 8, 12, or even 16 has a higher chance of making it to the table, so they're going to be over-represented compared to higher damage values. Or would be, anyway, if reality ran off of GURPS rules.

Originally Posted by Tomsdad

Yep, that's another way to go although if the concern is people aren't bleeding out and dying quickly enough in RAW you might want to set the death roll at say -2 or even -3. Otherwise on a straight HT roll you have lot of people at those stages who'd otherwise just be dead by RAW.

It would also only kick in once you've lost enough HP to qualify for a death roll.

I was saying this would be tracked in addition to bleeding. Basically, rather than death checks having three possible results - "fine" (success), "mortally wounded" (failure by 1 or 2), and "dies instantly" (failure by 3 or 4, or any failure once mortally wounded) - we'd add in some more possibilities - will die in hours, minutes, or seconds - between results two and three.

And, yes, this would result in fewer instant deaths, but really I don't think instant death is all that common. Also, as Douglas Cole notes, how quickly someone dies (or even if they die, often) only really matters for PC's and important NPC's, and even if it means sacrificing a little realism, I think the higher potential for interesting/dramatic results is worth it.

[Tomsdad]

Originally Posted by Varyon

...



I was saying this would be tracked in addition to bleeding. Basically, rather than death checks having three possible results - "fine" (success), "mortally wounded" (failure by 1 or 2), and "dies instantly" (failure by 3 or 4, or any failure once mortally wounded) - we'd add in some more possibilities - will die in hours, minutes, or seconds - between results two and three.

And, yes, this would result in fewer instant deaths, but really I don't think instant death is all that common. Also, as Douglas Cole notes, how quickly someone dies (or even if they die, often) only really matters for PC's and important NPC's, and even if it means sacrificing a little realism, I think the higher potential for interesting/dramatic results is worth it.

I'm fine with instant deaths being less common (sorry didn't mean to give a different impression). My point was that if the concern is people aren't bleeding out fast enough this house rule would only take effect once you reached a -1xHP. Which might take bleeding at the usual rate to reach in some cases.

But I take your point, what this would do is show some people dying by bleeding out instead of them just dropping dead instantly.

[David L Pulver]

Originally Posted by Polydamas

We are saying that basing damage on projectile diameter and just projectile diameter is a fundamentally misguided idea. It would create results like a .22 Long Rifle (5.6×15mmR) round doing the same damage as a 5.56 x 45 mm NATO round with (from Wikipedia) ten times the energy. "

If you were messing about with something like this, you'd want to base it on bullet size rather than just bullet diameter, because unless you're firing something like an APDS round it won't stay stable in the body upon hitting flesh. On a purely theoretical basis, I have read that most bullets (excluding special ammo types) tend to execute a single 180 degree turn within flesh. Frank Chadwick had a well-sourced essay on this in one of the Traveller or Twilight 2000 designer note articles (I think you can find it reprinted in the original edition of Fire, Fusion, and Steel).

So... the tissue destruction would channel and damage - assuming the round has sufficient kinetic energy to penetrate DR and through enough flesh, and didn't hit bone - might be something like:


Max injury = "bullet diameter in mm x bullet's length to width ratio x 0.5 x hit location modifier" . The length to width ratio is about 2 for most pistol ammo (including .22 LR, which is shaped like a pistol bullet) and about 4 for most rifle ammo, 1 for musket balls, etc.; you can find specific stats by looking it up if you want).

Note that this is the bullet, not the cartridge length. Examples:

.22 LR pistol round = 5.6 x 2 x 0.5 = 5.5
9mm pistol round to torso = 9 x 2 x 0.5 = 9
.45 pistol round to torso = 11.4 x 2 x 0.5 = 11
5.56mm rifle round to torso = 5.6 x 4 x 0.5 = 11
7.62mm rifle round to torso = 7.6 x 4 x 0.5 = 15
.50 MG round to torso = 13 x 4 x 0.5 = 26.

Of course, in reality, say, the 5.56mm rifle round will have more kinetic energy than, say, a .45 and so is more likely to shatter bones and such (or perhaps do hydrostatic shock if it hits a closed system like the skull) so the way GURPS does it of having it inflict a higher damage than merely basing it on wound channel is quite reasonable. I think that's what Frank also concluded for GDW's own game.

Personally, I'd stick with the current rules (or some variant of them like the ones I proposed) as it simplifies the issues of damage on a partial penetration (e.g., firing against an unarmored foe, etc.)...

[Anthony]

Originally Posted by David L Pulver

On a purely theoretical basis, I have read that most bullets (excluding special ammo types) tend to execute a single 180 degree turn within flesh.

For a conventional bullet that fails to expand or fragment that's the stable direction, but failing to expand or fragment is a pretty big caveat. Also, it's mostly redundant with blowthrough, any bullet that gets stopped in tissue deposits all of its energy and will cause nearly constant tissue destruction at any given bullet mass and velocity.