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Old 12-12-2020, 01:20 AM   #11
Say, it isn't that bad!
 
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Default Re: Base gun damage on calibre and gun size; armor divisor on kinetic energy?

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Originally Posted by RyanW View Post
It also seems to suggest (assuming I'm reading it right) that an AP-74 in .32 ACP would do the same damage as an M-14 in 7.62 NATO, which is just a completely nonsensical result.
Great; a problem has been identified. How do we fix it?
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Old 12-12-2020, 01:21 AM   #12
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Default Re: Base gun damage on calibre and gun size; armor divisor on kinetic energy?

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Originally Posted by Ulzgoroth View Post
You want High Tech p. 162. Optional Wounding Rules box, heading Body Hits.
Thanks; good to know.
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Old 12-12-2020, 05:05 AM   #13
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Default Re: Base gun damage on calibre and gun size; armor divisor on kinetic energy?

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Originally Posted by Say, it isn't that bad! View Post
I don't have enough info to even begin discussing this, save to say that the cube in square-cube law, is probably a not a great measure of hit points for a biological creature. After all, making a human twice as tall, wide, and thick, doesn't multiply the intervening mass between their vital organs and their skin by x8, but rather, by x2.
And indeed, if you look at B558, you'll see that hit points scale with the cube root of mass, which is (assuming shape is constant) proportional to height, thickness, etc.

GURPS' hit points are a good reflection of how hard it is to reach the vitals of a target, but not a good reflection of how hard it is to carve them up one small piece at a time. This is why they give decent results when dealing with attacks of the right 'size' for the target they're attacking (e.g. tank gun vs tank), but allow rifles to shoot up ships of the line far too easily.
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Old 12-12-2020, 07:54 AM   #14
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Default Re: Base gun damage on calibre and gun size; armor divisor on kinetic energy?

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Originally Posted by Say, it isn't that bad! View Post
Great; a problem has been identified. How do we fix it?
Honestly not sure how to fix it within the system you proposed. You simply must account for the fact that penetration depth, and therefore velocity, is more than a minor factor.
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Old 12-12-2020, 12:02 PM   #15
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Default Re: Base gun damage on calibre and gun size; armor divisor on kinetic energy?

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Originally Posted by Say, it isn't that bad! View Post
Great; a problem has been identified. How do we fix it?
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. I think GURPS' model works pretty well on human-sized targets (it has issues with large vehicles). To get something better on human targets, I would look for authors with domain expertise in trauma surgery, hunting, and ballistics.

David L. Pulver finally wrote up his forum house rule for the "machine gun vs. galleon" problem in Pyramid #3-34 "Extreme Damage".
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Old 12-12-2020, 03:20 PM   #16
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Default Re: Base gun damage on calibre and gun size; armor divisor on kinetic energy?

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And indeed, if you look at B558, you'll see that hit points scale with the cube root of mass, which is (assuming shape is constant) proportional to height, thickness, etc.
I blame the lack of sleep. :)
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Originally Posted by Rupert View Post
GURPS' hit points are a good reflection of how hard it is to reach the vitals of a target, but not a good reflection of how hard it is to carve them up one small piece at a time. This is why they give decent results when dealing with attacks of the right 'size' for the target they're attacking (e.g. tank gun vs tank), but allow rifles to shoot up ships of the line far too easily.
Polydamas notes a solution in Pyramid 3/34 below.
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Originally Posted by RyanW View Post
Honestly not sure how to fix it within the system you proposed. You simply must account for the fact that penetration depth, and therefore velocity, is more than a minor factor.
I would be hesitant to call it a "system". That word applies much more, well, systematization, than it actually contains or is implied. And, as I'll note below;
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Originally Posted by Polydamas View Post
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.
The problem has been identified; it doesn't need to be restated - it needs to be fixed. I don't know how to adjust for projectile velocity. Telling me the problem is that projectile velocity is not taken into account, over and over again, is not actually helpful. I know that. I cannot fix it.
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Originally Posted by Polydamas View Post
I think GURPS' model works pretty well on human-sized targets (it has issues with large vehicles). To get something better on human targets, I would look for authors with domain expertise in trauma surgery, hunting, and ballistics.

David L. Pulver finally wrote up his forum house rule for the "machine gun vs. galleon" problem in Pyramid #3-34 "Extreme Damage".
Thanks; that is a useful resource.
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Old 12-12-2020, 03:21 PM   #17
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Default Re: Base gun damage on calibre and gun size; armor divisor on kinetic energy?

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Originally Posted by Say, it isn't that bad! View Post
The problem has been identified; it doesn't need to be restated - it needs to be fixed. I don't know how to adjust for projectile velocity.
Using rules as written does an okay job at that.
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Old 12-12-2020, 04:53 PM   #18
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Default Re: Base gun damage on calibre and gun size; armor divisor on kinetic energy?

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Originally Posted by Say, it isn't that bad! View Post
The problem has been identified; it doesn't need to be restated - it needs to be fixed. I don't know how to adjust for projectile velocity. Telling me the problem is that projectile velocity is not taken into account, over and over again, is not actually helpful. I know that. I cannot fix it.

Thanks; that is a useful resource.
Well, you are proposing to replace a model where damage is proportional to the square root of energy times a factor based on the projectile diameter (see eg. Doug Cole's "Interior and Terminal Ballistics for GURPS," pyramid_2002/2002/0523.html) with one where its based on the projectile diameter. That is where the problem comes from.

I think to create something just as simple as and more realistic than Doug's model, you would need domain expertise in those subjects I discussed. Interior ballistics ("wounding") is a subject where lots of highly educated or experienced people scream at each other without coming to a consensus, beyond that a human being is likely to be in worse shape after being shot by a .50 BMG at 100 metres than a 5.56 mm NATO, and in worse shape if hit with the 5.56 mm NATO than a .32 ACP. I don't have that domain expertise.

I am not saying that its obvious that those ~ 8mm ish military rifle rounds from before 1914 do three times as much wounding as a 9 x 19 mm Parabellum, just that GURPS gives broadly reasonable results when humans and human-like characters get shot.
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Old 12-12-2020, 05:11 PM   #19
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Default Re: Base gun damage on calibre and gun size; armor divisor on kinetic energy?

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I am not saying that its obvious that those ~ 8mm ish military rifle rounds from before 1914 do three times as much wounding as a 9 x 19 mm Parabellum, just that GURPS gives broadly reasonable results when humans and human-like characters get shot.
I might caveat that down to get shot once with small arms.

Handling for getting hit with a cannon may be iffy and the way multiple hits accumulate is often criticized.
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Old 12-12-2020, 09:39 PM   #20
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Default Re: Base gun damage on calibre and gun size; armor divisor on kinetic energy?

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Handling for getting hit with a cannon may be iffy and the way multiple hits accumulate is often criticized.
Well, if a human being gets hit with a KE round from a cannon in GURPS they normally lose whatever part was hit, and that is reasonable.

Replacing HP ablation with tracking individual wounds is probably worth putting to the side since its separate from modelling individual wounds. The "light machine gun quickly destroying a large wooden ship by HP ablation" problem is related.
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