Over the past, in various GunDay posts, I’ve taken a look at the various Ultra-Tech weapons with a mind to both determining the feasibility of the weapons, and also checking their performance.

One of the more interesting posts, to me at least, was a ground-up redesign of a service pistol. The “ideal” pistol seemed to fire a 5.9mm projectile of unique engineered construction, which basically fired an advanced projectile that combined the AP capabilities of a tungsten tip along with a base that the tip gets pushed in to, which expands like the petals of the Ranger SXT modern-day JHP in order to enlarge the wound channel of the projectile to greater than 10mm, the threshold for pi+.

That gave us a projectile that wound up doing 2d (2) pi+, which wounds like a .45ACP and penetrates like a carbine, with a 20-round capacity that disappeared into a standard pistol grip.

Along the way, I also took a look at the Liquid Propellant (LP), Electrothermal-Chemical (ETC), and Electrothermal-Kinetic versions of various rifles, and found out (honestly, to my surprise) that all three were feasible with the right assumptions.

This particular article will take from all of those technologies in order to come up with a competitive TL9 rifle that’s an actual upgrade over TL8, and puts the right amount of power into the hands of the standard infantryman. Continue reading “Ultra-Tech Rifle: From the ground up”

GURPS telescopic sights work fairly simply. Each doubling of magnification gives a +1 bonus if you aim for a number of seconds equal to that bonus. So the “valid” scopes are x2, x4, x8, x16, etc. If you have a x1.5 scope, like the minor magnification on the Steyr AUG, you get nothing (+0 to Acc). If you have a x3 magnifier stacked in front of a collimating sight and use it as a telescopic sight, you get +1.

Them’s the breaks of breakpoints. Sometimes something is sub-resolution.

I was pondering based on an appropriately named thread on the SJG forums if there is a slightly different way to handle such odd powers: simply rewrite the Size and Speed/Range Table for your scope’s magnification, which is another way of saying calculate range penalties based on the effective range after accounting for magnification. Continue reading “Weak and Odd Scopes”

A brief digression into advanced conventional gun technology in GURPS Ultra-Tech.

There are two advanced technologies for firearms in GURPS Ultra-Tech. Liquid Propellant slugthrowers improves piercing damage by +1 per die (about 28%) with the boosted velocity version, and there’s a low velocity option that cuts damage in half, but we don’t care that much about that. Electrothermal-Chemical weapons increase damage by 1.5x. There are also Electothermal-Kinetic weapons, discussed in a Designer’s Notes for Ultra-Tech, Fourth Edition article, which are even more badass, multiplying damage by 2x.

What does that mean in terms of weapon design?

The Ballistics Model

My model – and remember, all models are wrong, some are useful – takes the peak pressure and maintains it for a certain distance down the barrel. This adds Pressure x Barrel Bore Diameter x Burn Distance in energy to the bullet: a straight-up application of energy equals force times distance. After that, it assumes that the propellant is all burned, and that the chamber and barrel and bullet form a pressure vessel, with the instantaneous pressure calculated using the ideal gas law. One can then calculate the instantaneous force at a given length down the barrel, and sum the product of that force over the distance – you’re performing an integration: E = Integral of F dx.

That’s wrong.

It just is. It’s not unusable, but it’s a simplification. It neglects the non-ideal component of the pressure equation, and it really ignores the fact that as the bullet is driven down the barrel, there is an opposing force of friction acting to retard the projectile. So while in real life, there’s an optimal barrel length after which more barrel is a hindrance to velocity, my model assumes that the bullet will continue to be accelerated pretty much forever.

That it falls off over distance, though, means that you need more and more barrel to actually get a GURPS-useful boost in velocity. So in practice, while it’s “wrong,” it’s not so wrong by so much that it doesn’t provide a useful and self-consistent model. Perfect? No. Usable? Yah.

But given the way that the program works, there are really only a few ways to add energy to the projectile. Continue reading “Ultra-Tech Firearms: Liquid Propellant and ETC”

In the last installment, a few of the basic weapons from the Rifles section of GURPS Ultra-Tech were examined. The basic premise was to see if the designed stats make sense, and evaluate them against an assumed mission statement: deliver 3d-6d injury after penetrating whatever armor the target is wearing. The typical foe was assumed to be a TL8 trooper wearing roughly DR 35/10d worth of hard/soft armor combination. This might be the TL8 Assault Vest + Trauma Plates (DR 12/5 + 23) or Advanced Body Armor (the generic form of DragonSkin, assumed to be as effective as the manufacturer claims).

Last time, we covered the basic Assault Rifle, and a derived hunting rifle firing the same ammo, the gatling carbine, and the 15mm payload rifle.

Today we finish up with some oddities, large-caliber specialty weapons that are either overdesigned or mis-applied in many cases. Continue reading “Gunday Continued: Ultra-Tech Rifles (Part 2)”

The rifle is the mainstay combat smallarm, given to every trooper. The current situation in the USA and the rest of the NATO countries have the primary projectile being the 5.56x45mm cartridge in various forms, and the “rest of the world” usually either uses the heavier and slower 7.62x39mm cartridge from the AK-47, or the small-caliber upgrade that is the 5.45x39mm from the AK-74. All of these more or less eke about about 5d: The 5.56x45mm M193 cartridge (the 55-grain/3.5 gram version) basically defines what 5d is in GURPS (and also happens to be about right – that bullet/rifle combo – the 55gr projectile at about 1000m/s from a 20″ barrel – punches through about 1/4″ of mild steel). The AK-47 is given 5d+1 in High-Tech, and the AK-74 a “downgrade” to 4d+2.

My own calculations are slightly different here, but only slightly. The 7N6M 5.45x39mm is a 53gr projectile at 880m/s, for 16.8 points of damage: 5d-1 is probably the best fit here; the penetration of 6mm of armor plate at 300m that is claimed (and the Rockwell C core hardended to Rc 60) might speak to a 1.5 armor divisor if such were still used. The AK47 bullet comes in at 19 points of damage, or 5d+1, as listed, at 122gr and 722m/s. My M193 comes in hot based on energy and diameter – it should penetrate for 19.3 points of damage, but empirically does not do so; some quick calculations show that the bullet is probably operating at close to it’s maximum coherence energy, so much kinetic energy in the projectile that the bullet itself can’t take the impact. Either that or (which is more likely) my formula is off by a bit. Either way, all of these come in at roughly 5d.

All that being said, what is enough injury? 3d injury is enough to take a regular Joe with 10HP and have them risking a KO; 6d is a death check. If your foes are human – and that’s the default assumption here – anything more than that is for two things: hitting at range, because you need to reach out and touch someone there, or punching through armor.

For the second, in GURPS, the best way to get armor defeat into the design is by bullet construction, that is to say, armor divisors to knock the protection down, followed by enough kinetic energy to defeat the remaining DR and the threat. For range, again, bullet construction is key, as high aspect ratio projectiles will hold their velocity (and thus damage) better. Retaining full ballistic performance (in terms of the GURPS 1/2D metric) to somewhere between 300 to 500m seems to fit the bill for the man-portable battlefield weapon category, and that’s basically the sweet spot for the 5.5mm type weapons, and the 7.62x39mm also fall in that range – my calculations put all three in the 400yds 1/2D range. That’s because of the relatively low sectional density of the 5.45mm round, and the high cross section of the 7.62mm one.

Battlefield Personal Weapon: Goals

So, the goals here for evaluating the old designs, and developing new ones, will be to improve on the 1/2D range (which also means that velocity loss by using shorter barrels will be somewhat mitigated) into the realm of the older battle rifle range (500-700yds), provide for a (2) armor divisor through bullet design (which will almost certainly mandate some sort of high-density core), and deliver 3d-6d injury after penetrating body armor.

The question of how much armor seems a legit one: modern trauma plates with a woven fiber armor backing will frequently provide about 10d worth of protection – DR 35 – from the plates alone, backed by the woven armor. The typical threat that this is gauged against seems to be the .30-06 M2 AP bullet, which hits for about that penetration.

So any design that’s notionally TL9 should probably stand up well against that level of ballistic threat.

Special Applications Rifles: Goals

The other set of weapons that will exist are what one might call rifles for special applications. Sniping, anti-materiel usage, and payload weapons all fit the bill here. These will put a premium on accuracy, as their usually hefty ammo does not lend well to carrying a lot of it. It will also be a place where versatility will come into play, as the projectiles start to get large enough that explosive, homing, and other special devices become practical and perform well.

Let’s Get To It

That’s a lot of pre-amble: let’s see how the rifles in the book do.

Ultra-Tech Standard Rifles

The book as written provides seven rifle-class weapons. All are assumed to be caseless, and they come in a few flavors. There’s a 5.7mm weapon that fires the same projectile as the PDW discussed in the prior write-up. There are two 7mm designs, two 10mm, a 15mm anti-materiel rifle, and a 25mm payload rifle. Let’s break ’em down. Continue reading “Sunday is GunDay: GURPS Ultra-Tech Rifles”

Idle conversation on the Discord chat about a full-auto .50 BMG rifle (as opposed to a machinegun) led to the comment that for sufficiently strong and large races or creatures, they really should be kitted out with battle rifles in sufficiently impressive calibers.

I mean, why wouldn’t a large-enough race make a rifle capable of firing 14.5mm KPV rounds?

Now, it’s been a while, but I don’t think a character’s ST has any impact on a weapon’s stat line.

Let’s look into fixing that. Continue reading “Rcl and ST in GURPS”

Continuing with my exploration of redesigns of the slugthrowers presented in GURPS Ultra-Tech, the next step is to look at submachine guns (SMGs), and Ultra-Tech (sensibly) includes Personal Defense Weapons (PDWs) in this category. However, if one looks at my prior articles, a raw-stats look at the four Ultra-Tech pistols, as well as some heavy design and less-heavy mechanics look at a ground-up TL9 pistol concept, you can see there’s already been some groundwork laid that should influence the following examination.

Prior Art

What concepts have been introduced?

  • TL9 10mm ammo has a base damage of 3d+2 pi+ out of a 4.5″/115mm and delivers around 1,100J of energy
  • There is a family of combustible case 7.8mm ammunition that deliberately targets GURPS breakpoints to deliver 2d+1 pi damage from an 85mm barrel, and 2d+2 pi from a 145mm barrel as a service pistol
  • An integral suppression system probably weighs about 0.1 lbs per 50mm of barrel
  • There’s a high-tech ammo type that was shown as an example of a TL9 combustible case or caseless telescoped cartridge. It uses a long bullet that expands to 75% of the length of the bullet in diameter. Call this CCTAPX (see-tap-ex) for combustible-case telescoped expanding. It’s cost per shot, though, is probalby 10x normal.

What is an SMG/PDW, anyway?

Ultra-Tech uses a fairly conventional classification of weapons, putting SMGs (which it defines as 10mm full-bore pistol rounds from a rifle-shaped platform) and PDWs in one group . . . but classifying short-barreled rifles, the carbine family, along with rifles. Continue reading “GunDay: GURPS Ultra-Tech SMGs and PDWs”

There’s an interesting problem – or at least an observation – when looking at the near-future slugthrowers from GURPS Ultra-Tech. The weapons themselves are a mixed bag of “well, it must be better!” and “there’s hardly any way that can happen.” It’s understandable, but leaving that aside, a futuristic pistol is a problem no matter how you slice it.

Why? The presumption of evolving threats, and a natural asymptote in the evolution of a design that debuted, fundamentally, in around 1900. The broom-handle Mauser C96, the M1900 Browning, and of course the M1911 Colt .45 ACP are all basically TL6 designs that evolved through two tech levels (in GURPS terms) to arrive at the early 21st century darn near as improved as they’re going to get.


One of the things one has to realize about a pistol is that they’ve always been secondary weapons. They were a one-shot (or even six-shot, in the US Civil War) first-strike to be wielded along side a saber, the primary weapon, initially. Then they were an officer’s weapon or signature, carried by commanders partially in order to remind them that their role was to direct troops, not engage in personal heroics.

Side note: I’m not necessarily making that up. I knew, personally, a Navy SEAL commander who was in Viet Nam. He was the course leader for the McKinsey and Company “mini-MBA,” and a great guy. He was quirky – he went swimming five times a day – but he told great stories, and his charisma and leadership were palpable. Naturally, I engaged him in conversation, and he told me that he rarely (maybe not ever) carried a weapon larger than a pistol, for that exact reason. His troops were there to kill the enemy; he was there to direct his troops. Staring over a gunsight robbed him of strategic vision. Hrm, says I.

But the thing about a pistol is that it’s not a primary weapon. As the old joke goes, “if I were expecting trouble, I’d have brought my rifle.” It’s a defensive or backup weapon that you can have with you all the time. While there’s no question a pistol can seriously kill you, it’s not a “serious” weapon for offensive purposes in nearly any case [1].

So we need to define what the mission of the weapon is. And I’m going to be pretty restrictive about it.

  1. It needs to be something you can carry with you at all times, comfortably. This probably limits total weight and size
  2. In many cases, it needs to be something small enough to carry concealed at all times, and be comfortable doing so
  3. It needs to pose a credible threat to an unarmored person
  4. It needs to be accurate and controllable enough to be used in two or three round salvos; if it’s worth shooting, it’s worth shooting twice
  5. It should hold as many bullets as possible without violating rules 1-4

Note how I don’t say “it should penetrate body armor.” Punching through armor is an offensive task. If you really want to stretch it, you can say that it should potentially be able to incapacitate someone through light armor, and by light we’re probably talking about car doors or casual protection – probably no more than DR 8, maybe even as low as DR 4. If the threat is wearing more than that, you need a rifle.

What does “incapacitate” mean? Heck, it probably means a single vitals hit will make you start rolling for unconsciousness. That’s an average penetrating damage of about 1d+1 pi. Asking a “casual” hit to the torso to do that will put the requirement of base damage in the 3d to 3d+2 range . . . which is 10.5 to 12.5 points of damage. With a pi+ bullet, that’s 2d or 2d+1.

That’s a reasonable ask in either case. Continue reading “The TL9 Pistol – Design Directions (GURPS)”

GURPS Ultra-Tech is a nifty book full of some fine inspiration. It is, however, a victim of being one of the first Tech books out there from fourth edition, and one that tried to be a few things at once, possibly while it was being written, possibly during playtest, and certainly during the post-playtest rewrites that occurred.

The projectile weapons are . . . in need of some work. There are some notable issues for the weapons, and honestly what they’re in need of is a redesign, rather than a rationalization. So, without further ado, here are some thoughts.

I’ll redesign each of the four TL9 pistols in the book, trying to keep close to as many of the stats as possible, but changing the ones that make no sense. Continue reading “Sunday is GunDay: GURPS Ultra-Tech Pistols”