Help a noobie understand critical hits

[Colonel__Klink]

Originally Posted by Ulzgoroth

Why are you sure about that?

Because physics lol. A 55 grain projectile 1/5th of an inch in diameter (that's what .223 refers to. "caliber" is a measurement of how wide the bore is in inches.) is not the same as a 4 lb, 4 inch wide cutting edge smashing into the rib cage. Some projectiles like the 5.56 have great kenetic energy but low momentum energy when compared (that's sort of the crushing blunt trauma effect you get from things like slings throwing heavy projectiles stopped by soft armor. )

This isn't media fantasy land where someone with an anti gun agenda is overstating the effectiveness of the ar-15 / M16 (I don't bother with the nonesense lie that they are two "very different rifles", in the USMC I was trained to fire my m16 semi auto only anyway, Save for a different trigger put in a differently cut lower receiver they are the same rifle.) It's a projectile that works but it doesn't obliterate the target. It's not as lousy in performance as pistol cartridges but you still see plenty of documentation of requiring several hits to down a target if something vital has not been hit. There's a reason why in the USMC we are trained to shoot multiple shots instead of fire and assess.

But that's another discussion altogether than gameplay mechanics.

Originally Posted by whswhs

I was wondering that myself. The kinetic energy of a 5.56mm rifle round is in the neighborhood of 1800 joules. A human fist blow has a lot less energy than that; I've seen various estimates, but if you set aside blows from heavyweight boxing champions, it looks as if the order of magnitude is about 1/10 as much. I'd expect an axe to have less kinetic energy than a bullet.

We see a lot of kinetic energy measurements. It's one way to understand energy. Another way is momentum energy. Momentum energy can help you understand from different perspectives, like how slings could and DID kill people wearing gambeson and mail even though the armor stopped the projectile easily. Compared to even low power handguns a sling provides very little kinetic energy, but they kill quite easily with lead projectiles even without hitting the face or head. It's kind of fascinating.

[Ulzgoroth]

Originally Posted by Colonel__Klink

Because physics lol. A 55 grain projectile 1/5th of an inch in diameter (that's what .223 refers to. "caliber" is a measurement of how wide the bore is in inches.) is not the same as a 4 lb, 4 inch wide cutting edge smashing into the rib cage. Some projectiles like the 5.56 have great kenetic energy but low momentum energy when compared (that's sort of the crushing blunt trauma effect you get from things like slings throwing heavy projectiles stopped by soft armor. )

Physics lol is about the right description for this analysis...

Originally Posted by Colonel__Klink

But that's another discussion altogether than gameplay mechanics.

It would be, except you're complaining about ways the mechanics don't agree with what you think is realistic.

And while you can certainly aim to make the rules serve your expectations, the expectations aren't necessarily right.

Originally Posted by Colonel__Klink

We see a lot of kinetic energy measurements. It's one way to understand energy. Another way is momentum energy. Momentum energy can help you understand from different perspectives, like how slings could and DID kill people wearing gambeson and mail even though the armor stopped the projectile easily. Compared to even low power handguns a sling provides very little kinetic energy, but they kill quite easily with lead projectiles even without hitting the face or head. It's kind of fascinating.

"Momentum energy" is not a thing. It's just momentum.

[Farmer]

Originally Posted by Colonel__Klink

Everyone seems offended I would dare to pare down the weapon damage exactly as you recommended ;P.

Not the weapon damage, the actual weapons. And no one is against that.

An alternative, if you want it to feel a little bit more like "That Other Game" is to provide "free" "Heroic Hit Points". These are the "scratches and bruises" hit points that don't really hurt you that absorb the initial attacks that hit you. You could issue 1 per 25 character points, for example, or whatever you feel works to get the flavour of the campaign that you want.

[mlangsdorf]

Originally Posted by Colonel__Klink

The survivable guns sounds shockingly close to what I was thinking. I have most pistols in the 1d range and most assault rifles as 2d(2) weapons.

A crappy little .32 being 1d6-1 giving a 50% chance of a roll of 2 or less which won't penetrate a heavy leather jacket in my equipment list (dr 2) . Surprisingly... that's fairly realistic

It's half damage and armor divisor 2, so that .32 pistol does 1d-1 (2) pi-, and has a 33% chance of doing 1 damage and failing to penetrate a DR 2 heavy leather jacket. Otherwise, it does 2, 3, 4, or 5 damage vs effective DR 1 and normal humans take 1 or 2 injury.

Originally Posted by Colonel__Klink

Much like I'm trying to figure out how to make calculating all the wound modifiers bearable.

Pi- is divide by 2. Cutting and piercing+ are divide by 2, then add by the initial value. Impaling and piercing++ are multiply by 2. In practice, on the table, it's pretty bearable.

Okay, Injury Tolerance means you sometimes need to divide by 3, 5, or 10 but none of those are hard.

Originally Posted by Colonel__Klink

What really got me on this trip against the damage model was seeing how pathetic something like vampire fortitude which requires 16 points in the power, 10 fatigue points spent AND a skill roll against a M:VH skill (that they have to pay points out of the wazoo for) in order to activate

The damage model is working fine IMO. Your implementation of vampires doesn't seem very good, so I'd go back and redo that. It's been literally decades since I cared enough about WW games to remember how their stuff worked, but I'd still recommend redoing your vampires before redoing the game's damage model.

Originally Posted by Colonel__Klink

Armor in the game TL8+ has to start having absolutely INSANE levels of DR to compensate for weapons hitting with 7-8 dice as an example. Even though frankly a 5.56 bullet if you're being realistic isn't going to hit someone harder than a big ol axe to the chest....

Well, it factually takes around 9mm of steel plate to protect against a 7.62mm rifle round, and 9mm of steel is at least 3 times as thick as any historical steel plate armor. So while I can't say as to whether a big axe is going to do more damage to unarmored human torso than a rifle bullet, I will say that the axe is going to penetrate less steel plate than the bullet will, and GURPS DR is based on penetration.

Originally Posted by Colonel__Klink

Celerity (vampire haste) was easier to fix. That originally just gave additional attacks and a move bonus.

Extra Basic Move +5 and Enhanced Dodge +2 turns the average man from a Dodge of 8 (25% success) to a Dodge of 15 (90% success), as well as doubling his running speed. I'd start there. You should probably spin off a thread to talk about your templates for PCs: I think there's a lot of advice that could be provided there.

Originally Posted by Colonel__Klink

As a basic template I was imagining that my players would all have combat reflexes (+1 defense) and high pain threshhold. My understanding is that removes the defenses halved debuff when they have low HP correct?

It prevents the shock penalty when you're injured, but not the Move and Dodge reduction for being below 1/3rd HP. You may be thinking of its improved version, Supernatural Durability.

Originally Posted by Colonel__Klink

Sadly there doesn't seem to be much more to help other than dumping into HT , Dex and finally HP. High stat character not skill and HEAVY into 18 HT or something.....

I've seen plenty of swashbucklers with DX 15, HT 13, HP 11, Acrobatics-16, Luck, Enhanced Dodge 1, Combat Reflexes, Basic Speed 7, and Dodge 12 jump into combat and use good tactics and ability to avoid 4-5 attacks each round: Acrobatic Dodge gets them up to a 14 versus the most dangerous attack, and then they've got Luck to fix a bad roll on the next 3 or 4 rolls versus a 12.

[Farmer]

Originally Posted by whswhs

I was wondering that myself. The kinetic energy of a 5.56mm rifle round is in the neighborhood of 1800 joules. A human fist blow has a lot less energy than that; I've seen various estimates, but if you set aside blows from heavyweight boxing champions, it looks as if the order of magnitude is about 1/10 as much. I'd expect an axe to have less kinetic energy than a bullet.

Of course it's not just about the energy. P=MV (Momentum = Mass x Velocity) but also P = F/A (Pressure = Force / Area). That bullet has a much higher Pressure number than the fist. We also need to consider things like Sheer ratings (bullets can shear through tissue and bone, fists can't. Then there's how the bullet acts once it's inside. Is it a hollow point, for example, expanding and causing more internal damage? Internal damage and punctures (shearing) is far more likely to cause a permanent or life threatening injury.

I know you know all this, I'm making the point for the OP.

[Colonel__Klink]

Originally Posted by Farmer

Not the weapon damage, the actual weapons. And no one is against that.

An alternative, if you want it to feel a little bit more like "That Other Game" is to provide "free" "Heroic Hit Points". These are the "scratches and bruises" hit points that don't really hurt you that absorb the initial attacks that hit you. You could issue 1 per 25 character points, for example, or whatever you feel works to get the flavour of the campaign that you want.

Pairing down the weapon selection was an option in the start but I decided it would be... pretty lame to have a campaign where the primary weapons are pipes, bats and an OCCASIONAL .32 pocket pistol that makes everyone tremble in terror when it's brought out.

Where's the fun? Where's the action and cool stuff? I have to have cool stuff! WHy am I planning a fantasy campaign if I hold back all the cool stuff? lol.

Originally Posted by Ulzgoroth

Physics lol is about the right description for this analysis...

It would be, except you're complaining about ways the mechanics don't agree with what you think is realistic.

And while you can certainly aim to make the rules serve your expectations, the expectations aren't necessarily right.

"Momentum energy" is not a thing. It's just momentum.

Lol you're right it is momentum. I never really used it before! I just knew of it surprisingly because of watching demonstrations of the example I used, slings. "This math calculation shows a big number" doesn't always mean it's going to put a man down better was the point. Poking a little hole in someone is obviously not as effective as splitting em wide open which was the point.

So when people say "but it's realistic" I ask "why is it that melee weapons are so garbage in comparison?" (again, a 5.56mm rifle works but it's nowhere near the kind of trama as SPLITTING THEIR RIB CAGE OPEN WITH AN AXE.) Which is how I keep getting pulled back into attacking the realism of it all even though I'm not terribly concerned with realism. My campaign has vampires, magic, super cyborgs, immortal eldrich beings. I don't care about realism too much. If I did I would be doing some boring mercenary campaign or something and everyone dies in five minutes apparently.

[Ulzgoroth]

Originally Posted by Colonel__Klink

Lol you're right it is momentum. I never really used it before! I just knew of it surprisingly because of watching demonstrations of the example I used, slings. I'm not too good with physics but having been in the USMC, been an armorer, then going to school as a trained gunsmith I'm preeeettttyyyyy familiar with various cartridges and effectiveness. "this math calculation shows a big number" doesn't always mean it's going to put a man down better was the point. Poking a little hole in someone is obviously not as effective as splitting em wide open which was the point.

So when people say "but it's realistic" I ask "why is it that melee weapons are so garbage in comparison?" (again, a 5.56mm rifle works but it's nowhere near the kind of trama as SPLITTING THEIR RIB CAGE OPEN WITH AN AXE.) Which is how I keep getting pulled back into attacking the realism of it all even though I'm not terribly concerned with realism. My campaign has vampires, magic, super cyborgs, immortal eldrich beings. I don't care about realism too much. If I did I would be doing some boring mercenary campaign or something and everyone dies in five minutes apparently.

Deep wounding being more effective that surface wounding seems to be pretty well known.

Really it seems like the problem in the comparison here is less your expectation about the bullet (which GURPS agrees won't always put someone down - depending on exactly which rules picks you're using it might even usually not) but your expectation that hitting somebody with an axe makes them double-plus-dead.


Which from the not caring about realism side surely would be just as 'un-gameable' as the bullet one-shots. I'm not sure who you ask for experimental data relating to hitting unarmored humans in the chest with an axe though.

[Varyon]

Originally Posted by Colonel__Klink

Because physics lol. A 55 grain projectile 1/5th of an inch in diameter (that's what .223 refers to. "caliber" is a measurement of how wide the bore is in inches.) is not the same as a 4 lb, 4 inch wide cutting edge smashing into the rib cage.

Velocity matters - gently pressing against that axe blade isn't going to accomplish much, after all. 5.56x45mm NATO out of a 20 inch barrel is moving at around 1000 m/s, or a bit shy of Mach 3. That 4 lb axe blade certainly has a lot more mass - it's about 500x heavier than that 55 grain bullet. It is faster than 500x slower, so will indeed have more momentum - a baseball bat swing (which should be comparable to an axe swing) is typically around 35 m/s, so we're at around 1/30th the speed, for around 17.5x the momentum. In terms of knockback and blunt force trauma, the axe is going to be more effective than the bullet - but in terms of tissue damage in the case of a penetration, the bullet is going to cause more of that, at least so long as it doesn't overpenetrate too much.

One of the issues here is that overpenetration failure mode for the bullet. Realistically, it's possible for that bullet to go through a part of the body that doesn't really matter much, at least not immediately. But with somewhere around 5d pi (which is what that round typically deals in GURPS), there's not a lot of room for that - even a low roll of 5 damage is a rather significant wound (only a point shy of a Major Wound), and you're less likely to roll that than you are to roll a 3 on 3d6! A possible houserule that might work for you here is lwcamps' Variable Blow Through, found here, alongside some other tweaks for impaling, piercing, and tight beam burning. Notably, an SM+0 character has a blowthrough cap of 2d - meaning whenever they are shot, the basic damage won't exceed whatever they roll on 2d for that shot. On average, that will mean 7 basic damage (which would then be modified by projectile size - boosted to 10.5 Injury, rounded down to 10, for pi+ for example), but it could mean as little as 2 (a hit to the love handles) or as much as 14 (a diagonal shot through the bulk of the torso).

[Farmer]

Originally Posted by Colonel__Klink

Because physics lol. A 55 grain projectile 1/5th of an inch in diameter (that's what .223 refers to. "caliber" is a measurement of how wide the bore is in inches.) is not the same as a 4 lb, 4 inch wide cutting edge smashing into the rib cage. Some projectiles like the 5.56 have great kenetic energy but low momentum energy when compared (that's sort of the crushing blunt trauma effect you get from things like slings throwing heavy projectiles stopped by soft armor. )

Energy of a 5.56mm / .223 round at muzzle is about 1,650nm with a front area of about 25mm^2.

An axe (a decent sized hand axe) is about 110nm and an equivalent frontal area of an axe is harder to define, but clearly the surface area increase rapidly as it penetrates. So it has less energy and a great area, meaning the pressure is less. This changes depending on the striking strength of the wielder, of course. That's why axe rarely leave exit wounds.

Both can create lethal wounds, and if a bullet exits then not all of its energy is transferred into the target. But to say that a bullet has low momentum energy (which is a tautology) is not correct.

I think you need to reconsider your understanding of energy and how it is measured. Look at momentum and pressure in particular, but then also consider how that translates into damage of a body.

[Varyon]

Originally Posted by Colonel__Klink

(again, a 5.56mm rifle works but it's nowhere near the kind of trama as SPLITTING THEIR RIB CAGE OPEN WITH AN AXE.)

A 5.56mm rifle bullet to the ribcage is more likely to kill than an axe. That axe is going to bruise your vital organs, possibly even perforate them. The bullet shards are going to shred your vital organs. You're not terribly likely to survive either (if the axe hit hard enough to split the bones anyway; you need a strong attacker and/or a good hit to do more than crack them), but the bullet is much more likely to kill you. If that's where it hits, that is - those cases of people being relatively unaffected from being shot typically involve hits elsewhere (or involve people who are actually in the process of dying but don't realize it; GURPS doesn't model this very well, admittedly).