How to Stat Ghost in the Shell Style Hypervelocity Ammunition

[GURPS Fox]

Originally Posted by Rupert

It has to be higher than that, because modern tank guns reach that and they have massive muzzle blasts, so there's plenty of energy and pressure still in the propellant gasses.

The Russians are claiming a little over 2 k/s for their new 125mm gun and ammo, but that being hype and exaggeration is quite possible.

From what I gather, by 1.8km/s you're getting inefficient when it comes to things like powder burn (think the M551 Sheridan's caseless round problem, the powder didn't burn efficiently enough, and it caused problems like cookoff while you load a new round in). In addition, you could only get 2km/s with sabots, and even then, you'll start to get inefficient.

So, here is an 'HV Ammo Ruleset' I've cooked up with your guys' input:

• HV Ammo is only available to 'conventional' guns built using tech from TL8 or later.
• HV-compatable weapons have a 1.1x weight multiplier to simulate the added features to make the weapon take the pressures and punishment of an HV round.
• In ANY Non-HV TL8 or higher weapon that uses HV Ammo, increase the Malf. by two steps in the initial magazine and increase Malf. by one step per additional magazine. If the weapon is made at tech levels less than TL8, turn the weapon and magazine into a grenade of similar weight (to simulate a catastrophic cook-off).
• Base ammo (i.e., FMJ/Solid) is 1.25 times the damage and range. All rounds have a 1.5x modifier to the cost of the round. Example: a 5.56NATO round from an HV-compatible M16 rifle will get a damage roll of roughly 6d+1 instead of the usual 5d.
• Other modifiers (like ETC or saboted ammunition) can be applied to HV ammo.