[Ultra Tech] Increased Firearm Power with TL

[Rupert]

Originally Posted by Varyon

Are modern small arms using propellants at this limit? I know there has been talk of using high explosives as propellants, but maybe those aren't shelf-stable or are otherwise unfeasible, and we're stuck with modern smokeless. Or maybe there could be a dramatic breakthrough of some flavor.

Not 'talk of' - stabilised high explosive was the propellant for the G11's careless ammo, and it was accepted for service. The compound they came up with has a much higher cook-off temperature than conventional smokeless propellant, which solved the problems they were having with cook-offs due to the loss of heat sinking via metal cases (and also possibly because of the sealed nature of the mechanism).

[Varyon]

Originally Posted by David L Pulver

Often a significant reduction in weight while keeping damage/velocity the same will result in the weapon kicking about a lot more and thus harder to hit things with rapid fire (higher Rcl) but the ST not changing much (because you've made the weapon lighter, so it's easier for your ST to manage even if it does kick more.)

An issue here is that, if the weapon is difficult to keep on target because of increased kick, that Rcl boost is something that being sufficiently-strong should be able to mitigate it, but GURPS is rather clear that high ST does nothing for dealing with Rcl. Also, anecdotally I've heard plenty of people claim that a heavier weapon is easier to shoot - not just for rapid fire, but simply for plinking. And, this makes sense if recoil maps to momentum but controlling it maps to kinetic energy - a weapon that's half the weight would have the same recoil momentum (matching the momentum of the bullet and propellant), but twice the kinetic energy (a half-weight weapon would be pushed back twice as fast to have the same momentum, while halving weight while doubling velocity results in twice the kinetic energy).

Personally, I think a higher-resolution version of the MinST rules for firearms would have two MinST's - the ST necessary to comfortably hold the weapon at the ready (dependent entirely on weapon weight; I'm assuming it would be a bit lower than what would be needed to use the firearm as a melee thrusting weapon), and the ST needed to handle the recoil (which is a function of the weapon's recoil energy, and thus for a given performance goes up as weapon weight goes down), but generally just using the greater of the two (someone who meets the first but not the second could hold the weapon steady, but not fire it without running into issues; someone who meets the second but not the first would need to rest the weapon on something before firing), although not quite meeting the latter might allow for normal weapon use with increased Rcl. But I have no idea how to really set these MinST's...

Originally Posted by David L Pulver

To address the original point: certainly one can make a case that ammunition chemistry will get better and material strengths also improve, and so making a rule that this is what happens every TL is quite justifiable!

Yeah, that was my thought process here - I just wasn't certain if the damage boosts were on the right track.

Originally Posted by David L Pulver

In general, I wouldn't put something like that in a core "Ultra-Tech" book because it's a pain to recalculate all the ancillary numbers, any more than I'd raise damage of swords and modify breakage risks by a few percents or pluses every TL after TL8 to account for similar gradual improvements in steel alloys.

My thought here was more to have an entry like this:

"Extra-Powerful (+P) (TL9)
Ammunition that makes use of higher chamber pressures and more propellant is available. +P typically results in x1.1 to Damage, Range, and MinST. Due to material improvements, firearms at higher TL's can handle even higher pressures, in the form of Ultra-Powerful (+UP) ammunition. Exact power varies, but at TL 9 +UP can increase the multiplier to x1.2, at TL 10 it can increase it to x1.3, at TL 11 it can increase it to x1.4, and at TL 12 it can increase it to x1.5."

Originally Posted by Rupert

A longer case, and/or overall cartridge length is not an issue in terms of the tech. It's a small issue when it comes to use (but really not one at all for battle rifles and machineguns). Mostly it's an issue with manufacture because it means all new receivers and bolts, etc., and the US arms industry is very heavily invested in standard M16 sized parts, and they don't have enough length for a longer (say .30-06 or 7.62x54mmR) cartridge.

The concern here is that what I'm talking about isn't the standard ammunition for the weapons - rather, it's the +UP I outlined above, an option like modern +P but with even more propellant and higher chamber pressure. If your weapon normally takes ammunition that basically contains as much propellant as can fit in the round's volume, there's no room for +UP (or even +P) rounds to fit, unless those use a more dense/powerful propellant than your default weapon. For cased ammunition, this means you would need empty space in the default cartridge. For caseless, my headcannon for those is basically that you have the propellant proper mixed in with a mostly-inert, consumable buffer, and +P/+UP would involve increasing the ratio of propellant to buffer. But how likely is it that you could get up to +20%, +30%, +40%, and even +50%? That last basically calls for the normal cartridge to be only ~40% "full" of propellant (like modern pistol cartridges, apparently) so that it can fit enough to get to x1.5 damage. Of course, you could have it be the case that many UT firearms could theoretically handle +UP but there simply are no such cartridges (because there's no room for more propellant), while certain brands specifically use oversized cartridges so that they can accommodate +UP. Just throwing names and numbers out there, but maybe both Small Arms International LLC and YeetCannon FTW make comparable pistols in 10mmCL, but while SMI's pistol uses 10x15mmCL, YC's pistol instead uses 10x25mmCL. 10x15mmCL has no +P or +UP options, because it basically has as much propellant as it can, but 10x25mmCL can manage up to +UP x1.5 damage because its default is only at ~35% capacity.

[johndallman]

Originally Posted by Varyon

Personally, I think a higher-resolution version of the MinST rules for firearms would have two MinST's - the ST necessary to comfortably hold the weapon at the ready (dependent entirely on weapon weight; I'm assuming it would be a bit lower than what would be needed to use the firearm as a melee thrusting weapon), and the ST needed to handle the recoil (which is a function of the weapon's recoil energy, and thus for a given performance goes up as weapon weight goes down) . . .

The first of those would be affected by ergonomics: horribly front-heavy guns, or ones that have weight sticking out to the left or right, would have higher MinST1.

But Phoenix Command and madness lie along this route.

[Varyon]

Originally Posted by johndallman

The first of those would be affected by ergonomics: horribly front-heavy guns, or ones that have weight sticking out to the left or right, would have higher MinST1.

But Phoenix Command and madness lie along this route.

The rules from LTC2 on MinST for melee weapons simply have poorly-balanced weapons (like those with a heavy weight at the end) have +1 to MinST, particularly well-balanced ones have -1 to MinST. Of course, I'm not overly fond of those rules, as it seems like the weight one should be able to wield should scale linearly with BL, and that's not the case there. Something like "You can wield poorly-balanced weapons that weigh up to 10% BL, relatively-balanced weapons that weigh up to 15% BL, and well-balanced weapons that weigh up to 20% BL" should be workable (for an ST 10 character, that would be 2 lb, 3 lb, and 4 lb, respectively). What counts as poorly/regularly/well balanced would simply be up to the GM. Because they're just held steady rather than being used to strike, firearms should probably have lower MinST - maybe treat them as around 70% nominal weight if one-handed, 50% if two-handed (LTC2 has two-handed weapons weigh 2/3 normal, which is right around 70%). The bigger issue is recoil, and I have no idea how you'd start to work that up... and it may not be something that can really be simplified down enough to be usable.