How to Stat Ghost in the Shell Style Hypervelocity Ammunition

[GURPS Fox]

Originally Posted by The_Ryujin

Multiply damage and range by 1.1×, cost by 1.5×. they're probably at lest APHC, add AD (2) and reduce pi damage down one category, cost 2×. For my write up I used a hypothetical Armor Piercing Dense Cored round triples cost but does everything that APHC does and increase damage by 1.2×.

So, what would APHC rounds look like in GURPS 3e, or am I overlooking that it possibly shares the definition of APCR?

[Fred Brackin]

Originally Posted by GURPS Fox

So, what would APHC rounds look like in GURPS 3e, ?

In 3e it'd be just the regular AP with its' AD of (2). APHC is a 4e High tech thing where APHC is an improved version of AP.

[GURPS Fox]

Originally Posted by Fred Brackin

In 3e it'd be just the regular AP with its' AD of (2). APHC is a 4e High tech thing where APHC is an improved version of AP.

Good to know.

So, if I'm getting this right, using a 'conventional' (i.e., not liquid or electrothermal chemical propellant) propellant, I multiply the range and damage by 1.1 and round cost by 1.5...

... meaning that an HV-M16 would have a 5d+2 compared to the original 5d of the regular M-16. That is, if I did the math right.

This is odd, for Spacebattles (which has a tendency to analyze stuff like this until its an atomized dead horse) calculated (including the static friction co-efficient of rubber on wet concrete as the stand-in for sneakers on wet concrete) that to push a full-borg (which is implied in-verse as increasing one's weight by double) a foot requires roughly double the force of a 7.62NATO round, for a 9mm machine pistol. HV ammo is incredibly hot by all modern standards.

[Fred Brackin]

Originally Posted by GURPS Fox

G

This is odd, for Spacebattles (which has a tendency to analyze stuff like this until its an atomized dead horse) calculated (including the static friction co-efficient of rubber on wet concrete as the stand-in for sneakers on wet concrete) that to push a full-borg (which is implied in-verse as increasing one's weight by double) a foot requires roughly double the force of a 7.62NATO round, for a 9mm machine pistol. HV ammo is incredibly hot by all modern standards.

To e a little less technical about it but to look at firearms history we see that recoil is heavily dependent on gun weight.

To handle the recoil of a .30 caliber rifle cartridge takes the weight of a BAR (17 to 22 lbs empty depending on model). When they first tested the much lighter M14 (10.9 lbs empty) on full auto from a standing position the recoil left the gun vibrating very heavily (high Gurps Rcl) and the user walking backwards. The very similar FN-FAL couldn't be comtrolled from a standing unbraced position and historically such weapons were not used full auto in such a manner.

That might already be something like our cyborg skid but if you put rounds of that power in an 8.8 lb Uzi things would obviously be even worse. It would at least cancel out the effects of the cyborg weight and ST increase.

[GURPS Fox]

Originally Posted by Fred Brackin

To e a little less technical about it but to look at firearms history we see that recoil is heavily dependent on gun weight.

To handle the recoil of a .30 caliber rifle cartridge takes the weight of a BAR (17 to 22 lbs empty depending on model). When they first tested the much lighter M14 (10.9 lbs empty) on full auto from a standing position the recoil left the gun vibrating very heavily (high Gurps Rcl) and the user walking backwards. The very similar FN-FAL couldn't be comtrolled from a standing unbraced position and historically such weapons were not used full auto in such a manner.

That might already be something like our cyborg skid but if you put rounds of that power in an 8.8 lb Uzi things would obviously be even worse. It would at least cancel out the effects of the cyborg weight and ST increase.

Yeah, I actually figured as much. It would also explain why 'PDWs' in the Ghost in the Shell meta-verse utilize intermediate cartridges instead of high-velocity pistol rounds.

So, to push a -assumed- 100kg 'borg wearing sneakers a foot on wet concrete, you'll need 735 N (or, for those using moon-landing units, 165.23457374515561 pounds-force) of force. With 20 rounds being fired, that ends up having each round having 36.7 N (or, for moon-landing unit users, 8.250488240064232 pounds-force) of recoil (hence the double 7.62NATO comment). To give you an idea of just how over-loaded these rounds are, a 9mm Parabellum only gives 3.7 N (or, 0.831793092322552 pounds-force) in terms of recoil. That requires sending such a round at tremendous velocities (well above 1km/s minimum, though some calcs indicate that this can go as high as 11km/s, everyone agrees that's just plain insane as no conventional propellant can achieve such velocities).

That's pretty hefty, no matter what you say about it.

[Varyon]

Originally Posted by GURPS Fox

That requires sending such a round at tremendous velocities (well above 1km/s minimum, though some calcs indicate that this can go as high as 11km/s, everyone agrees that's just plain insane as no conventional propellant can achieve such velocities).

That's pretty hefty, no matter what you say about it.

As a note here, a 9mm bullet typically has a velocity around 350 m/s, and GURPS firearm damage typically scales linearly with velocity. So, determining what velocity would be required for that amount of recoil force will give you your damage. 1050 m/s (just above that 1 km/s minimum) would be 3x damage (as 9mm typically does 2d+2, that's 8d-1); 10,850 m/s (just below that 11 km/s maximum) would instead be 31x damage (80d-1).

Of course, I'll note that, if you're basing the "recoil pushback" off the garbage truck scene from the 1995 movie, I'm not certain that guy was a full body cyborg. He obviously had a neural interface (couldn't have had his brained hacked otherwise), and his jumps imply some leg enhancements, but I don't recall any indicators that he was extremely heavy (Motoko breaks off pieces of a building while scaling it in the scene, and severely dents the roof when she lands on it; he rocks some small boats when he jumps on them, but then a human of ordinary weight would similarly rock them when jumping off and landing from a few meters' height). Changing him to be of comparable weight (or perhaps a bit heavier) than a normal human will tone down the amount of power those bullets would need.

All that said, it's also important to keep in mind that GitS is rather cinematic; while I don't recall if it happens in the movie, it seems to be the kind of setting where someone would get thrown back a few yards from a point-blank shotgun blast. So you could interpret the recoil pushback to just be indicative of more recoil than normal, not that it would literally have enough recoil force to push the character back like that.

[The_Ryujin]

Yeah, Space battle's calcs tend to be kinda nonsense. If I recalled they tried to make the claim that the VTOL attackers were launching something around 5kt missiles at the 3rd angel in Evangelion back in the day based on diameter if the super simple sphere explosions the show used, failing to take into account not only how abstract they were rendered kinda made realistic calculations moot but the fact the small town the missiles were being set off over wasn't being affected all that much even by the missiles that went off near ground level. Common sense also kinda overwrites the idea they were spamming nukes as a first response heh.

And that's a key take away, even in a fairly realistic movie like 1995 Ghost in the Shell, the director is going to use visual short hand to get information across to the audience even if they have to cheat a little if it gets the point across better. How to let the audience know the bag guy loaded some spicy bois into his gun without telling them? Show the bad guy brace as hard as he can and barely not get pushed by by the recoil. Even if it doesn't make sense in reality, it gets the point across to an audience who might not be physics majors or gun nerds. HV ammo in the manga wasn't a super weapon, in fact the term HV is a US translation, they were just called overpower round (i.e hot loaded) in Japanese

[GURPS Fox]

Originally Posted by Varyon

As a note here, a 9mm bullet typically has a velocity around 350 m/s, and GURPS firearm damage typically scales linearly with velocity. So, determining what velocity would be required for that amount of recoil force will give you your damage. 1050 m/s (just above that 1 km/s minimum) would be 3x damage (as 9mm typically does 2d+2, that's 8d-1); 10,850 m/s (just below that 11 km/s maximum) would instead be 31x damage (80d-1).

Yikes.

Of course, I'll note that, if you're basing the "recoil pushback" off the garbage truck scene from the 1995 movie, I'm not certain that guy was a full body cyborg. He obviously had a neural interface (couldn't have had his brained hacked otherwise), and his jumps imply some leg enhancements, but I don't recall any indicators that he was extremely heavy (Motoko breaks off pieces of a building while scaling it in the scene, and severely dents the roof when she lands on it; he rocks some small boats when he jumps on them, but then a human of ordinary weight would similarly rock them when jumping off and landing from a few meters' height). Changing him to be of comparable weight (or perhaps a bit heavier) than a normal human will tone down the amount of power those bullets would need.

All that said, it's also important to keep in mind that GitS is rather cinematic; while I don't recall if it happens in the movie, it seems to be the kind of setting where someone would get thrown back a few yards from a point-blank shotgun blast. So you could interpret the recoil pushback to just be indicative of more recoil than normal, not that it would literally have enough recoil force to push the character back like that.

True, however it is something of a baseline we can use.

Originally Posted by The_Ryujin

Yeah, Space battle's calcs tend to be kinda nonsense. If I recalled they tried to make the claim that the VTOL attackers were launching something around 5kt missiles at the 3rd angel in Evangelion back in the day based on diameter if the super simple sphere explosions the show used, failing to take into account not only how abstract they were rendered kinda made realistic calculations moot but the fact the small town the missiles were being set off over wasn't being affected all that much even by the missiles that went off near ground level. Common sense also kinda overwrites the idea they were spamming nukes as a first response heh.

Given the Evangelion rebuilds, that's not ludicrous as you think.

And that's a key take away, even in a fairly realistic movie like 1995 Ghost in the Shell, the director is going to use visual short hand to get information across to the audience even if they have to cheat a little if it gets the point across better. How to let the audience know the bag guy loaded some spicy bois into his gun without telling them? Show the bad guy brace as hard as he can and barely not get pushed by by the recoil. Even if it doesn't make sense in reality, it gets the point across to an audience who might not be physics majors or gun nerds. HV ammo in the manga wasn't a super weapon, in fact the term HV is a US translation, they were just called overpower round (i.e hot loaded) in Japanese

That's true. In addition, even the dubs don't have HV ammo as a superweapon, just either they're either outright insane using it in a weapon that isn't designed for it (GitS Movie) or just 'nasty toys' to the party (GitS:SAC).

When you think about it, having 3x is the absolute maximum, somewhere between 1.5-2x being the more practical end.

[Fred Brackin]

Originally Posted by GURPS Fox

When you think about it, having 3x is the absolute maximum, somewhere between 1.5-2x being the more practical end.

None of it is "practical". You might be aiming more at "physically possible".

1600 meters per second might be that physically possible limit for anything even vaguely like gunpowder. Some rifles would hit that limit at around 1.5x. P

[The_Ryujin]

3× is kinda crazy, like TL 10 ETC might justify 1.5×. 3 times the damage from boosted velocity means that the bullet is traveling 9 times faster! Now if you want to get crazy you can say that HV ammo is as good as 1st gen ETC ammo (1.25× damage under the current draft and fits my research) and treat them as APFSDSDU rounds. APFSDSDU gives a AD (2) and boosts damage by 1.7× (from a combination of higher muzzle velocity, density and lower crosssectional area) and doubles range but reduces pieing damage by 1 step. I'd also have HV ammo worsen Malf. by two steps unless the gun is designed to fire them (maybe 1.5× cost).

Let's take a 9mm round fired by an Uzi which is 3d-1 which averages 9.5 pts of basic damage. This becomes 9.5 × 1.25 × 1.7 or ~20.2 pts (!) which translates into 6d-1 (2) pi-. With this HV 5.56mm will become 10d+2 (2) pi-. This will give you a nice cinematic HV feel.