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Old 05-09-2017, 12:23 PM   #41
Varyon
 
Join Date: Jun 2013
Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

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Originally Posted by weby View Post
But if one uses your proposed model where just failing to penetrate causes 1 point.
An easy solution here is to base the "just failed to penetrate" off of basic damage, without armor divisors in play. An armor piercing round that fails to penetrate does nothing, even if it were only a point shy, while a normal round that just fails does 1 point of injury. Now you'll never have the issue of a lighter armor piercing round causing more deformation than a heavier round.

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Originally Posted by Tomsdad View Post
EDIT: sorry just looking again at the second second section of this, I'm no sure what you mean when linking MinST to Knock back? And I'm not sure a 10g bullet travelling 830m/s will knock back a human sized target (in lots of armour) a yard if it collides but doesn't penetrate. But then knock back in GURPS is a lot of different things.
For the first, that was in reference to the action/reaction bit - that is, if a bullet can push a person back a yard then firing it should push that same person back a yard as well. As Knockback Threshold is based on HP, and HP is based on ST, it makes some sense to assume the typical wielder of a weapon will have HP equal to or exceeding MinST, which will give us the amount of Knockback the character would suffer from firing the weapon without properly bracing himself for the recoil (there are no rules for adjusting Knockback when there is bracing involved, but it would make sense to reduce Knockback in such cases). To my knowledge, there aren't any firearms that the Knockback calculated using my proposed houserule would be enough to knock the firer back a yard or more (there's a musket in HT that comes dangerously close - 4d+1 pi++ and ST10 - but none that actually reach this point). Bows and crossbows might be a different story, but that's an issue with the unrealistic ST-based damage table.

For the latter, I calculated the impact damage using the Collisions rules from Tbone's GULLIVER rules, which are designed to be more realistic than the default GURPS rules. I only calculated it for three projectiles, however - the 5.56x45mm, 7.62x39mm, and .50 BMG - and extrapolated from there, so the actual crushing damage of other bullets may not be as suggested in my houserule. Unrealistic Knockback results may be more an issue with the Knockback rules than with the crushing component of bullets.

Quote:
Originally Posted by Hellboy View Post
B378's Knockback rules could benefit from some expansion.
Post #4 of my previously linked thread does a lot of this, by essentially giving every attack a crushing component (which would have Knockback associated). Having attacks that are partially blocked only have Knockback from the portion of the damage that is blocked is a logical addition.

Quote:
Originally Posted by Tomsdad View Post
Somethings also need to be adjusted on an individual basis (a v.fine cutting sword that gets +2 damage for being extra sharp etc, shouldn't be better at knocking people back if it fail to get past DR)
Again, the previously-linked thread has this effect built-in.

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Originally Posted by Tomsdad View Post
*Equally I see no reason why swung imp attacks risk getting stuck, but thrust imp ones don't. I'd prefer to make it function of Imp damage in some way, as I also don't see why a 2 point Swung Imp injury is as prone to get stuck as a 12 point one (just as I don't see what 2 point swung Imp wound risks getting stuck, but a 12 point thrust imp wound doesn't)
With a swinging attack you have a bit of build-up of momentum during the swing, which you don't have for pulling it back out, so it's harder to pull back out than it was to initially put in. This isn't the case with thrusting. That's the idea, anyway - in reality it's certainly possible to get a thrust impaling weapon stuck so that it takes a moment to pull out, but (outside of barbed weapons) this is treated as below GURPS resolution.
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Old 05-09-2017, 02:56 PM   #42
Hellboy
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Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

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Originally Posted by Varyon View Post
Post #4 of my previously linked thread does a lot of this, by essentially giving every attack a crushing component (which would have Knockback associated). Having attacks that are partially blocked only have Knockback from the portion of the damage that is blocked is a logical addition.

Again, the previously-linked thread has this effect built-in.
Does anyone have a link to this thread? I'm not able to locate it here. Sounds interesting.


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Originally Posted by Varyon View Post
With a swinging attack you have a bit of build-up of momentum during the swing, which you don't have for pulling it back out, so it's harder to pull back out than it was to initially put in. This isn't the case with thrusting. That's the idea, anyway - in reality it's certainly possible to get a thrust impaling weapon stuck so that it takes a moment to pull out, but (outside of barbed weapons) this is treated as below GURPS resolution.
Your first sentence makes me want chances for swing/cut weapons to get stuck too, since we only have for swing-impale.

The only thing above GURPS resolution for thrust/impale seems to be stop-thrust :( I want it for everything... stop thrusts should just be more likely due to the higher damage they get from the guy ramming himself onto your spear.
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Old 05-09-2017, 03:43 PM   #43
Varyon
 
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Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

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Originally Posted by Hellboy View Post
Does anyone have a link to this thread? I'm not able to locate it here. Sounds interesting.
I linked it back in post #25 of this thread, but here it is again. As previously noted, post #4 of that thread is the relevant one (the main thrust of the thread is revamping combat skills, but there's some changes to damage and armor as optional rules).

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Originally Posted by Hellboy View Post
Your first sentence makes me want chances for swing/cut weapons to get stuck too, since we only have for swing-impale.
Sw/cut weapons are a lot easier to leverage out, so they'd be roughly as likely to get stuck as thr/imp. My experience with axes getting stuck in logs has it being problematic simply because the logs are so light you can pick them up with the axe - once they're stabilized in some way (putting a foot on it works well) they're typically perfectly easy to remove. This is getting quite a good distance afield from the topic of this thread - blunt trauma from firearms - so if you wish to continue this part of the discussion you'll probably want to start a new thread.
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Old 05-10-2017, 04:24 AM   #44
Tomsdad
 
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Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

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Originally Posted by Varyon View Post
...


For the first, that was in reference to the action/reaction bit - that is, if a bullet can push a person back a yard then firing it should push that same person back a yard as well. As Knockback Threshold is based on HP, and HP is based on ST, it makes some sense to assume the typical wielder of a weapon will have HP equal to or exceeding MinST, which will give us the amount of Knockback the character would suffer from firing the weapon without properly bracing himself for the recoil (there are no rules for adjusting Knockback when there is bracing involved, but it would make sense to reduce Knockback in such cases). To my knowledge, there aren't any firearms that the Knockback calculated using my proposed houserule would be enough to knock the firer back a yard or more (there's a musket in HT that comes dangerously close - 4d+1 pi++ and ST10 - but none that actually reach this point). Bows and crossbows might be a different story, but that's an issue with the unrealistic ST-based damage table.

For the latter, I calculated the impact damage using the Collisions rules from Tbone's GULLIVER rules, which are designed to be more realistic than the default GURPS rules. I only calculated it for three projectiles, however - the 5.56x45mm, 7.62x39mm, and .50 BMG - and extrapolated from there, so the actual crushing damage of other bullets may not be as suggested in my houserule. Unrealistic Knockback results may be more an issue with the Knockback rules than with the crushing component of bullets.
Ah OK I have to say I don't know those rules

I think my point is I'm not sure such a bullet can by itself push a target back a yard (so don't need to worry about pushing it's firer back a yard and so doesn't need to be tied to MinST)

A 7.62nato is going to have about 8.3 kg m/s momentum? That will push a 100kg target (say are reasonable sized man wearing enough torso DR to stop the bullet penetrating and other kit) back at 0.083 m/s. And that's an inelastic collision no friction etc.

However as said knock back is likely other things as well than just physics, but bullets don't have that much momentum

There was a thread that touched on this just recently (and my later rules suggestions were wrong because of this!)


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Originally Posted by Varyon View Post
Again, the previously-linked thread has this effect built-in..
Cool

Quote:
Originally Posted by Varyon View Post
With a swinging attack you have a bit of build-up of momentum during the swing, which you don't have for pulling it back out, so it's harder to pull back out than it was to initially put in. This isn't the case with thrusting. That's the idea, anyway - in reality it's certainly possible to get a thrust impaling weapon stuck so that it takes a moment to pull out, but (outside of barbed weapons) this is treated as below GURPS resolution.
Yeah I think tying it to damage done covers that (thrust damage being less than swung for that very reason)

Last edited by Tomsdad; 05-10-2017 at 11:25 AM.
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Old 05-10-2017, 11:45 AM   #45
Varyon
 
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Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

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Originally Posted by Tomsdad View Post
Ah OK I have to say I don't know those rules
You can find them on Tbone's Diner, or linked in my previously-linked thread, but they're a bit annoying to work out. I basically assumed the bullet was completely stopped by the collision (otherwise not all of the damage would have applied), and ignored the speed change suffered by the target (damage is actually based on the change in speed resulting from the collision), assuming the target was sufficiently large that this would be functionally 0. The end result is that the crushing component of a bullet is, in dice, W*V/1500, where W is weight in lb and V is velocity in mph. The annoying part, and why I didn't do it for more than three bullets, is that you need to use a weapon that's already statted in GURPS, look up muzzle velocity and weight, convert from ft/s (or m/s) and grains (or g) to mph and lb, and then run it through the calculation (and IIRC I didn't actually condense the equation as above, which made things even worse).

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Originally Posted by Tomsdad View Post
I think my point is I'm not sure such a bullet can by itself push a target back a yard (so don't need to worry about pushing it's firer back a yard and so doesn't need to be tied to MinST)
A big part of this is an issue with the GURPS Knockback rules. Realistically, knockback isn't some instantaneous effect like we see in GURPS (where the target moves the intervening distance instantly, but is treated as having constant velocity that would require them to take a full second to move this distance while being pushed back) - rather, it's a brief acceleration that adds some velocity to the target, and the target will either need to accelerate itself to negate it or let friction+gravity do that for it. Actually working that out is going to be pretty nasty in play, however. There's also the issue (related to your later statements, which I haven't included simply for space) that GURPS calculates knockback based on HP, rather than on mass - something that pushes a 100 lb object back at 1 yard per second should push a 50 lb object back at around 2 yards per second, but as HP scales by cube root rather than linearly, and knockback is based on HP-2, the 100 lb object has a knockback threshold of 7, while the 50 lb one has a knockback threshold of 5. Additionally, mass from gear and armor doesn't make a difference in GURPS. Again, it's a loss of realism for the sake of being easy to use in play.

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Originally Posted by Tomsdad View Post
There was a thread that touched on this just recently (and my later rules suggestions were wrong because of this!)
I'll give it a look.

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Originally Posted by Tomsdad View Post
Yeah I think tying it damage done covers that (thrust damage being less than swung for that very reason)
Having the damage roll (not counting adds from the weapon) be at or near maximum for thrust result in an impaling weapon getting stuck is something I've considered. Thrust attacks only get stuck on particularly strong attacks, while swing attacks won't get stuck on weaker attacks. I opted against it, due to the fact that I interpret damage rolls as often being more about attack placement than the actual force behind the attack (which I think will typically be much less variable than the dice indicate).
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Old 05-11-2017, 01:14 AM   #46
Tomsdad
 
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Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

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Originally Posted by Varyon View Post
.....



A big part of this is an issue with the GURPS Knockback rules. Realistically, knockback isn't some instantaneous effect like we see in GURPS (where the target moves the intervening distance instantly, but is treated as having constant velocity that would require them to take a full second to move this distance while being pushed back) - rather, it's a brief acceleration that adds some velocity to the target, and the target will either need to accelerate itself to negate it or let friction+gravity do that for it. Actually working that out is going to be pretty nasty in play, however. There's also the issue (related to your later statements, which I haven't included simply for space) that GURPS calculates knockback based on HP, rather than on mass - something that pushes a 100 lb object back at 1 yard per second should push a 50 lb object back at around 2 yards per second, but as HP scales by cube root rather than linearly, and knockback is based on HP-2, the 100 lb object has a knockback threshold of 7, while the 50 lb one has a knockback threshold of 5. Additionally, mass from gear and armor doesn't make a difference in GURPS. Again, it's a loss of realism for the sake of being easy to use in play.
OK I have to say I agree there are likely issues with GURPS Knock back. I'm guessing rooted in the fact it's a gameable simplification of a complex effect that's going to involve more than just the physics of moving objects around by impact (and that itself is not simple thing to calculate when you factor other forces acting on the system). But that doesn't really detract from the point that 8.3 kg m/s is really not very much force here.




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Originally Posted by Varyon View Post
Having the damage roll (not counting adds from the weapon) be at or near maximum for thrust result in an impaling weapon getting stuck is something I've considered. Thrust attacks only get stuck on particularly strong attacks, while swing attacks won't get stuck on weaker attacks. I opted against it, due to the fact that I interpret damage rolls as often being more about attack placement than the actual force behind the attack (which I think will typically be much less variable than the dice indicate).
That's true but the range of the damage rolls is also pretty closely tied to the strength of the attack. The thing is there are also target specific factors in weather something gets stuck as well (generally bone placement, tissue type and depth of penetration) but also changing angles etc. So attack placement can be factor as well!

What doesn't help is that it's likely different placement factors will effect damage to the overall target (itself a pretty abstract thing) and the chances of getting stuck!

However if you wanted to remove placement as a variable, and worked on the assumption that placement is the overriding variable what gives the variation on damage rolls.
Maybe instead of taking the damage actually rolled, take the average damage of the attack. That would be maybe a more consistent measure of how initially powerful the attack is abstract. But I can see problem where glancing blows that barely connect would be boosted by this.

Last edited by Tomsdad; 05-11-2017 at 02:09 PM.
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Old 05-11-2017, 11:00 AM   #47
Varyon
 
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Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

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Originally Posted by Tomsdad View Post
But that doesn't really detract from the point that 8.3 kg m/s is really not very much force here.
It's not much momentum, but it's around 3.5 kJ force. A punch over 1 kJ is remarkable, so that rifle round should have more crushing damage than even a rather strong punch. The issue, of course, is that not all crushing damage is created equal - I believe a punch tends to have a good deal more momentum than a 5.56 NATO round, so the punch should cause more knockback. GURPS simply ties knockback to damage for the sake of simplicity, so things can fall apart a little here, but I don't think it does so overly much for the mild cinematic default of GURPS.

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Originally Posted by Tomsdad View Post
The thing is there are also target specific factors in weather something gets stuck as well (generally bone placement, tissue type and depth of penetration) but also changing angles etc. So attack placement can be factor as well!
Indeed. Part of my planned Overhaul is to basically replace* the damage roll with a roll to represent hit placement, for a similar effect (as well as possibly some add-on effects - a bullet to the arm isn't very likely to cripple unless it hits the bone, in which case it's very likely to cripple if it has decent damage; effects of hit placement on whether an impaling weapon gets stuck are possible as well), and which also dictates the damage cap. As it stands, a low-damage roll with high-powered rifle still does the character's full HP in injury, while the Overhaul would change this to a glancing blow.

*Characters with low skill still have a damage roll, but with normal damage as the best result - they are basically rolling to not screw up. I assume, absent attack options dictating otherwise (Defensive Attack, Committed Attack, or the range allowed by my Combat Posture Overhaul - which can be found on the blog in my signature), skilled combatants strike with consistent force. This isn't strictly realistic, but is close enough to justify not adding in another roll.
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Old 05-11-2017, 11:20 AM   #48
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Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

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Originally Posted by Varyon View Post
It's not much momentum, but it's around 3.5 kJ force. .
You should be ignoring kinetic energy or force or KJ or anything besides momentum.

The Mythbusters tried this. They hung a pig in a tactical vest on a hook so it could be knocked off by a very small transfer of momentum. Tori did it with a thrown baseball.

No gun they tried could duplicate that feat until maybe the shotgun slug and more clearly the .50 BMG. They had to replace the standard trauma plate with 3/4 of an inch of mild steel which the .50 BMG penetrated anyway.

Note that the .50 BMG did not cause the vested pig to fly backwards energetically. It probably only went back a quarter of an inch. Of course the thrown baseball didn't cause anything but the barest amount of backward movement either.

You sometimes see what is clearly Gurps Knockback on the football field but no reasonable bullet meets armor scenario will create any. 100 kg men at over 6 or 7 meters per second sometimes but no bullets.

So I wouldn't introduce massive house rules to "fix" this "problem". I certainly wouldn't think I could ever make it square with raw damage.
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Old 05-11-2017, 11:33 AM   #49
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Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

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Originally Posted by Fred Brackin View Post
You should be ignoring kinetic energy or force or KJ or anything besides momentum.
Apologies if I was unclear - my post was meant to defend the amount of crushing damage I suggested for bullets, and simply note that the high amount of knockback this results in is an oddity of the GURPS Knockback rules, which are already at least mildly cinematic. I was further indicating that the Knockback, while unrealistic, is probably within the realm of standard GURPS cinematics. Essentially, strong characters using weapons at or near the maximum of what they can carry around and fire will cause a yard or two of Knockback on a weaker character, provided the bullet is stopped by the target's armor. It's unrealistic, but not something that would seem out of place or comical in even a low-cinematic action movie, for example (it would be unrealistic in a movie that tries to be realistic, but the bulk of the audience probably wouldn't even notice).
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Old 05-12-2017, 01:18 AM   #50
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Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

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Originally Posted by Varyon View Post
It's not much momentum, but it's around 3.5 kJ force. A punch over 1 kJ is remarkable, so that rifle round should have more crushing damage than even a rather strong punch. The issue, of course, is that not all crushing damage is created equal - I believe a punch tends to have a good deal more momentum than a 5.56 NATO round, so the punch should cause more knockback. GURPS simply ties knockback to damage for the sake of simplicity, so things can fall apart a little here, but I don't think it does so overly much for the mild cinematic default of GURPS.
Your right, but I think that just really means you shouldn't be giving bullet Cr, but instead keeping them to Pi. Whoops, yes I'd been saying momentum for the last few posts but slipped to force in that last one, sorry ;-)



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Originally Posted by Varyon View Post
Indeed. Part of my planned Overhaul is to basically replace* the damage roll with a roll to represent hit placement, for a similar effect (as well as possibly some add-on effects - a bullet to the arm isn't very likely to cripple unless it hits the bone, in which case it's very likely to cripple if it has decent damage; effects of hit placement on whether an impaling weapon gets stuck are possible as well), and which also dictates the damage cap. As it stands, a low-damage roll with high-powered rifle still does the character's full HP in injury, while the Overhaul would change this to a glancing blow.
...
A couple of points:

Against a limb a rifle bullet won't do full HP in injury (it's capped at half HP*).

When it comes to rifle bullets even if they don't hit bone they can take a reasonably large chunk of flesh out (thanks in part to key holing**). However I do agree the practically automatic nature of them doing so is a problem. And shorter and less powerful pistol rounds are on average too capable of doing so as well.

One tweak here might be to apply doubling the threshold for dismembering / severing rule from HT "limb hits" (HT pg162) to the crippling threshold as well. That will not really effect a lot of rifle wounds, but will limit pistol rounds ability to do so a bit


*well OK half rounded up or half +1

**TBF This gets complicated as not all rifle rounds in all limbs will have the space/time to turn 90 degrees to get the largest wound track, lots of variables here! But equally crippling at it's most basic just means you disrupted the limb's ability to function enough for it not to be used. There are several ways you can do this in a limb without breaking a bone or ripping out entire muscles. But then that said limb's can keep working through a lot of damage as well (including broken bones)! Basically as ever with the effect of damage on people, lots of variables!

Either way If we're really looking at this I'd would adjust the crippling threshold for legs vs. arms, (legs and arms are rarely the same size/mass)

Last edited by Tomsdad; 05-12-2017 at 01:31 AM.
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