How to Stat Ghost in the Shell Style Hypervelocity Ammunition

[GURPS Fox]

Originally Posted by Fred Brackin

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

As far as I know, the absolute limit for 'conventional' gunpowder (i.e., nothing that uses things like electrothermal chemical propellants) is 1.8km/s.

Originally Posted by 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.

... wow... that's a lot of good information. This is why I like the GURPS community. Ask a question, and you'll have people showing up with the context and answer.

Originally Posted by Varyon

GURPS firearm damage typically scales linearly with velocity, so 3x damage is 3x velocity (or, rather, given we were looking at starting with velocity, it’s that 3x velocity means 3x damage). And as I got that 3x figure starting from a weapon that has a muzzle velocity of 350 m/s, you’d want to set your damage based on that; as 350 is the typical 9mm velocity, and 2d+2 pi is, IIRC, the typical 9mm damage, you’d triple that, for an average of 27 pi - which is 8d-1 pi.

So stronger than conventional 7.62NATO if we use the 3x modifier.

That’s still pretty crazy; I’d expect a weapon that is designed for it would have a lot of weight and probably a long bolt; if dude’s SMG had been using such monstrous rounds, it probably would have burst apart during the first salvo, rather than being able to at least fire a couple more magazines of normal ammo (but the way it treated cover implied it might have still been using HV).

Given Ghost in the Shell metaverse's general semi-rediculous materials science (the musculature of cyborgs are CNT muscle alone and can do things like take at least 200-meter drops and two M67 hand grenades at point blank with ease), it is likely that the weapon only fared as well as it did because it was a more modern version using modern materials. If the perp used an older model, it would have gone kaboom.

At least I'm not going full-on 6Commando (a webcomic based on Ogre, whose battlesuit weapons fire rifle rounds at roughly 3km/s using some hybrid of conventional rifles and gauss called 'mag-boosted' guns)...