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Old 05-08-2017, 05:29 AM   #21
DeathDaisy
 
Join Date: Sep 2011
Location: Sweden
Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

In Low-tech, there's a box on p. 102 named Blunt Trauma and Edged Weapons which might be relevant for this discussion too. It says that it's incredibly hard for a blade to cut through armor, so optionally, treat cutting damage as crushing unless the damage exceeds twice the DR of the armor.

The same could maybe be done with high-tech armor and high velocity projectiles to solve the problem Anthony and Ulzgoroth were talking about; if the attack doesn't exceed the DR by much, the damage is BABT and converted to crushing. This seems a pretty RAW way to do it, considering the LT-box.
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Old 05-08-2017, 05:42 AM   #22
Tomsdad
 
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Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

Quote:
Originally Posted by DeathDaisy View Post
In Low-tech, there's a box on p. 102 named Blunt Trauma and Edged Weapons which might be relevant for this discussion too. It says that it's incredibly hard for a blade to cut through armor, so optionally, treat cutting damage as crushing unless the damage exceeds twice the DR of the armor.

The same could maybe be done with high-tech armor and high velocity projectiles to solve the problem Anthony and Ulzgoroth were talking about; if the attack doesn't exceed the DR by much, the damage is BABT and converted to crushing. This seems a pretty RAW way to do it, considering the LT-box.
Thing is that would mean a DR25 Trauma plate (from HT) would turn up to 25 points of otherwise normally penetrating Pi damage into Cr damage?

Which would pretty dramatically change how such armour works in GURPS, it will also lead to some odd situations:

For instance given how over penetration normally caps Pi damage by HP, having it convert to Cr could lead to more damage being inflicted instantly in some cases!

With up to 25 points of Cr damage you also get some serious knock back

Last edited by Tomsdad; 05-08-2017 at 07:12 AM.
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Old 05-08-2017, 06:18 AM   #23
DeathDaisy
 
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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
Thing is that would mean a DR25 Trauma plate (from HT) would turn up to 25 points of otherwise normally penetrating Pi damage into Cr damage?

Which would pretty dramatically change how such armour works in GURPS, it will also lead to some odd situations:

For instance given how over penetration normally caps Pi damage by ST, having it convert to Cr could lead to more damage being inflicted instantly in some cases!

With up to 25 points of Cr damage you also get some serious knock back
I wasn't aware there was a damage cap on piercing attacks? Are you thinking of the overpenetration rules in campaigns? It says the attack overpenetrates if it does more damage than your DR+HP, but doesn't mention an actual injury cap as far as I can tell. But I might be missing something.

But anyway, if the number seems excessive, make it crushing for up to 1\2 DR for piercing attacks perhaps.
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Old 05-08-2017, 06:40 AM   #24
Tomsdad
 
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Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

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Originally Posted by DeathDaisy View Post
I wasn't aware there was a damage cap on piercing attacks? Are you thinking of the overpenetration rules in campaigns? It says the attack overpenetrates if it does more damage than your DR+HP, but doesn't mention an actual injury cap as far as I can tell. But I might be missing something.


Yep there's an over-penetration rule in High Tech for Torsos (basically injury is maxed at HP, but still counts at full value for Bleeding etc).

It stops high energy rifle bullets taking people to -1xHP or worse in one shot instantly. Bullet wounds even from high energy rounds don't really work that way unless they hit some pretty specific things.

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Originally Posted by DeathDaisy View Post
But anyway, if the number seems excessive, make it crushing for up to 1\2 DR for piercing attacks perhaps.
I think my issue is such rounds just won't do that much Cr damage.

I'm going to try Anthony's half and half suggestion with my allowing blunt trauma to counts as Cr for knock down tests, and see how it goes

Last edited by Tomsdad; 05-08-2017 at 07:37 AM.
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Old 05-08-2017, 08:00 AM   #25
Varyon
 
Join Date: Jun 2013
Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

Quote:
Originally Posted by DeathDaisy View Post
In Low-tech, there's a box on p. 102 named Blunt Trauma and Edged Weapons which might be relevant for this discussion too. It says that it's incredibly hard for a blade to cut through armor, so optionally, treat cutting damage as crushing unless the damage exceeds twice the DR of the armor.

The same could maybe be done with high-tech armor and high velocity projectiles to solve the problem Anthony and Ulzgoroth were talking about; if the attack doesn't exceed the DR by much, the damage is BABT and converted to crushing. This seems a pretty RAW way to do it, considering the LT-box.
GURPS armor and firearm stats are interrelated and based on real-world performance - RHA steel (the standard for penetration/protection tests) has DR 70 per inch, and firearm damage is based on what they can penetrate. A 5d pi rifle is one that's rated to penetrate 1/4 inches of RHA steel, and 1/4 inches of RHA steel gives DR 17.5 (average damage for 5d). Using Blunt Trauma and Edged Weapons would throw this off. Granted, there may be cause to give all armor split DR, and I did so as part of my Combat Skills Overhaul (the relevant post is #4, under the Blunt Trauma section), but that's more complicated than most are going to want at the table. Also, IIRC, that 70% DR figure was basically just pulled out of the air - I have no idea what the actual proportion should be.

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Originally Posted by Tomsdad View Post
For instance given how over penetration normally caps Pi damage by HP, having it convert to Cr could lead to more damage being inflicted instantly in some cases!
That isn't entirely unrealistic, although extremely unlikely. Because the armor completely stops the bullet, that means the armor+body must absorb all of the bullet's momentum, instead of just the portion represented with blowthrough. However, you basically need some fantasy material that gives way more DR against piercing than crushing (even Kevlar only has a 4x difference, which isn't enough to see the effect). Say you have DR 60/5 (60 vs pi, 5 vs cr). A piercing attack is capped at 10 HP injury, so with the 1/3 divisor (suggested in the linked thread, and also my previous post in this one) you reach that with a 45 damage piercing attack against the above armor (45 pi becomes 15 cr, which becomes 10 injury when DR is subtracted). Anything between 48 (11 HP injury) and 60 (15 HP injury) thus does a bit more injury.
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Old 05-08-2017, 10:23 AM   #26
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
...

That isn't entirely unrealistic, although extremely unlikely. Because the armor completely stops the bullet, that means the armor+body must absorb all of the bullet's momentum, instead of just the portion represented with blowthrough. ....
I think my issue is bullets just don't have that kind of momentum.

Look at the kind of knock-back you'd be getting here, and what that would mean for firing a gun that did that with Newtons 3rd law in action.
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Old 05-08-2017, 10:30 AM   #27
DeathDaisy
 
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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
Yep there's an over-penetration rule in High Tech for Torsos (basically injury is maxed at HP, but still counts at full value for Bleeding etc).

It stops high energy rifle bullets taking people to -1xHP or worse in one shot instantly. Bullet wounds even from high energy rounds don't really work that way unless they hit some pretty specific things.
Aha, I'll check it out, sounds like a reasonable rule.

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Originally Posted by Tomsdad View Post
I think my issue is such rounds just won't do that much Cr damage.
Fair enough, I'm far, far from an expert and just went with gameablity, so I'll concede :) Might still try it in my own games tho, see how it works out, maybe cap the damage at even less, just a few points or so.
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Old 05-08-2017, 11:03 AM   #28
Varyon
 
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Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

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I think my issue is bullets just don't have that kind of momentum.
Bullets usually don't have that kind of momentum. A bullet fired from a tank's main gun, or even "just" a mounted anti-materiel rifle, could very well have such. Like I said, it's not entirely unrealistic, just extremely unlikely, as the sort of impact pressures that would have to be involved will usually punch through the armor.

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Originally Posted by Tomsdad View Post
Look at the kind of knock-back you'd be getting here, and what that would mean for firing a gun that did that with Newtons 3rd law in action.
Look at the kind of damage you need for that knockback - my example called for a DR 60/5 armor before the effect came into play. You don't get this kind of performance with weapons that can be hip-fired. As for the action-reaction effect, I don't think there's a single weapon where MinST is low enough for an average hit* to knock the wielder back, and considering the shooter is going to be better braced for impact than the target, things should work out alright here. Yes, this does mean an M14 will, on an average-but-nonpenetrating hit (meaning he'd need to be wearing armor that would put Ned Kelly's to shame), knock an ST 10 character back one yard. Part of that is GURPS' unrealistic (but easy to use) knockback rules, of course, but for the modest cinematics GURPS defaults to, it doesn't seem like a bad rule. The lesser reduction for pi++ means you only need around 4d+2 to manage that knockback, which can be a bit more problematic, but not game-breakingly so.

*Higher than average damage with a firearm doesn't mean a more powerful bullet, it means hitting a higher-value target, impacting at a better angle, or similar.
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Old 05-08-2017, 11:04 AM   #29
Anthony
 
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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
That seems very precise in terms of RL conversion to GURPS, what are you basing that on?
It's actually just a conversion of RL to RL. Basically, the NIJ standards for armor specify a list of attacks that must fail to penetrate, and also specify a maximum amount of backspace deformation by listed attacks. The maximum appears to be 44mm, which is actually quite a bit; enough that a point of non-penetrating damage seems reasonable (this is actually a sort of reasonable general rule -- since the backface standards are consistent, just assume any attack that barely fails to penetrate does 1 point of blunt trauma, and ignore the existing rules for nonrigid armor).

However, level IV armor is rated to stop 7.62mm AP, and while there are no specific standards for resistance to weaker threats other than they also have to not get through, there's not really a plausible design for plates that suffers the same deformation against 5.56mm as it would against 7.62.
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Old 05-08-2017, 01:05 PM   #30
weby
 
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Default Re: High Amounts of non penetrating damage. Bullets VS Plate Carriers

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However, level IV armor is rated to stop 7.62mm AP, and while there are no specific standards for resistance to weaker threats other than they also have to not get through, there's not really a plausible design for plates that suffers the same deformation against 5.56mm as it would against 7.62.
Yes, but there are quite likely plausible designs that can stop 5.56 AP(avg pen 35) with less deformation than 7.62 ball(avg pen 24) as the strike energy of the 5.56 is so much smaller.
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