+Mark Langsdorf has an armor design system on his blog that is geared towards Dungeon Fantasy levels of cool. Good armor to match the very high damages that heroes can dish out.

Chatting with +Nathan Joy, who has played and GM’d with both Mark and myself in various games, he noted that it would be nice if Mark’s system produced a bit lower DR for the weight. 

I took a peek at Low-Tech, and that book lists DR 4 “fine mail” – the prototypical and historical value for DR for this type of armor in GURPS – as 15 lbs for just the torso. That means that covering yourself head-to-toe in DR4 mail would be about 46 lbs.

That’s about 11.5 lbs per point of DR, compared to the 6 lbs per point in Mark’s table (which, by the way, is formatted more sensibly as ‘a full suit,’ rather than making a full suit 305% of the armor value in the table as in Low-Tech).


So what if we doubled all the values? That doesn’t quite mesh with some very nice plate armor, though that might depend on how much DR it really had. Some breastplates were 3-4mm thick at the most robust part, and about half that at the thinnest. At DR 2-2.5 per mm for older steels, that’s a DR in the 6-10 range, so we benchmarked it as DR 8 weighing around 60-70 lbs. 8 lbs per point of DR seemed better and a nice value, and that was less than doubling would provide.


It was also a bit more than Mark would have liked (I shared this with him; he wrote BFA, after all), and so I tweaked it out a bit to match his expectations more.

OK, moving on to cost, looking around, again, at plate harness, we found estimates that equated to between six to twelve months pay for a skilled laborer was what harness could cost. We pegged that at between average and comfortable wealth, or, all said and done, about ten grand for a DR 8 full suit.

Then I did math. Not a lot, but I liked Mark’s low estimate of about $50-60 per point of DR for the natural hides and cloths. Again with the jiggering, if I wanted the low figure at roughly $60, and the high at $1,200, that meant a factor of 20 in cost for a factor of about 3 or 3.5 range in pounds per point of DR. Net/net, cost per point of DR should be about $1,035,000 divided by the lbs per DR to the 3.25 power.

That gives the modified table above, which I tweaked out to avoid nasty decimals.

The lighter per point of DR your armor is, the more you pay for it. If you want DF-quality armor at 6 lbs per point of DR . . . it can be had for about $3,000 per point of DR. So a DR 8 harness would cost $24,000 and weigh 48 lbs. 

That’s not crazy talk.

By eye, this table isn’t completely insane, either, compared to Low-Tech. Cloth and Silk would be about 5.3 lbs/DR for torso only, which is in the ballpark. Cost for Textiles at DR 1 torso-only would thus be about $11. DR 4 mail, torso only is 13 lbs (LT has 15) and costs $2,300 (LT has $900). Lightweight but very expensive, befitting something that was pretty darn labor-intensive.

So again, not insane. 

Looking at armor types, the natural ones are all less than $125 per point of DR. The metal ones are more expensive, with scale (small flat plates hammered out, available very early in time) costing less than the more labor-intensive mail, and still less than the finely-crafted full-plate harness.

Parting Shot


The table leverages Mark’s excellent “keep it basically simple” “Better Fantasy Armor” rules and scales it based on some real-world benchmarks (well, as real-world as 400+ year-old data can get) to achieve something that’s at least internally self-consistent. 

It can scale reasonably well, too. And if you want to find the cost for (say) casting Lighten on plate harness for 4 lbs per point of DR? Plug it into the formula, and you get a 32-lb., DR 8 harness at $91,500.

The issue you’ll run smack into here is that the Strength table gets pretty egregious about punching through armor at values that PCs have access to (and should). Lots of proprosed solutions for this, including dropping damage to a fraction of ST, as in my rescaling from very, very early in my blogging career. All of them nerf ST penetration one way or another.

What about different Tech Levels? TL4 to TL8 has a 3.25x difference in monthly pay, and materials and production methods get better. So divide, which means our DR 8 65-lb plate would be about $2,900. That is, again, not insane.

I’m sure there are issues here, but for a quick conversation, I like where it ended up . . . but since you can still swing at ST 17 for 3d with a broadsword, some method of dealing with that issue is recommended. 

The GURPS rules for hollow point or expanding bullets in GURPS are pretty simple: you pick up one level of increased wounding modifier in exchange for having an armor divisor of (0.5), meaning that your projectile is really quite poor at penetrating armor, but pretty good at injuring people.

So 2d+1 (0.5) pi- would normally average 8 points of penetration through armor, and 4 points of injury on an unarmored person. Against DR 4, on the average it would be blocked. Why one would fire off a pi- hollow-point is beyond me, of course – the example just shows how the rules work.

A 9mm FMJ would be 2d+2 pi normally, and thus do 9 points of armor penetration, 9 points of injury, and 5 injury through DR 4. A 9mm hollowpoint would (in RAW GURPS) would punch through only DR 4.5 on the average, and do 13.5 points of injury against an unarmed person. Only one point (on the average) would punch through DR 4, resulting in 1.5 injury.

A .45 ACP would normally do 2d pi+, and in hollowpoint will do 2d (0.5) pi++. So again, against an unarmored person, 7 points of penetration and 10.5 of inury in ball, and 14 in hollow point. Through DR 4, 7 won’t penetrate in JHP, but ball will do 4.5 injury.

In any case, the RAW is simple.


The Ballistic Calculator


My ballistics calculator handles things a bit differently. It recalculates penetration based on the expanded diameter of the projectile instead of applying arbitrary modifiers. This can produce truly monstrous wound channel modifier (though GURPS caps at pi++), but also gives a nice, straightforward damage reduction that isn’t quite as harsh as the (0.5) armor divisor.

Now, let’s look at three examples. A 1.3 expansion (typical of some .45ACP), a 2.0 expansion (which is typical of Jacketed Soft Point rifle bullets), and 1.65 (which works well for modern 9mm and .40 S&W that was engineered for large expansion).

  • A .45 ACP with no expansion has 2d with a 1.5 modifer. (7 points)
  • A .45 ACP wth a 1.3 expansion has 1d+3 with a 2.1 modifer (6.5 points, or )
  • A .45 ACP with a 1.65 expansion has 1d+2 with a 2.7 modifier (5.5 points, or -22%)
  • A .45 ACP with a 2.0 expansion also does 1d+2 with a 3.4 modifier

A 6.8x43mm would do 6d with a 0.7 modifier unexpanded

  • The 6.8 with a 1.3 expansion would do 5d+2 with a 0.9 (21 to 19.5, or -7%)
  • The 6.8 with a 1.65 expansion would do 5d with a 1.2 (21 to 17.5, or -17%)
  • The 6.8 with a 2.0 expansion would do 4d+3 with a 1.5 (21 to 17, or -19%)
So between soft and expanded, you’re looking at about -20% for effective hollow-points. That’s about -1.5 per 2d damage, regardless of caliber. If you want to account for soft bullets, it’s more like a (0.8) than (0.5).
So a 9mm would go to 2d pi+, and a 6.8mm would be 6d-4.5, which is 5d-1 pi+.
Against armor, it will tend to do a bit better than the RAW, but still worse than unarmored flesh.
The (0.8) will be annoying in play; I’d tend to ditch it, but if you can quickly just increase DR by 25% before figuring penetration, you’re good. 5d-1 pi+ carbine bullet vs DR 12? It becomes DR 15, and likely on the average will do 1.5 penetration, increasing to a bit over 2 points of injury on the average. By RAW, it’s 6d (0.5) pi+, and DR 12 goes to DR 24, and will almost always bounce.

Parting Shot

This is for extreme realism fans, and even so, the modeling work required to pull this off is probably more than most people need. But the RAW really nerfs the penetration abilities of JHP bullets, making them devastating against
unarmored targets, but utterly useless against any sort of armor. That’s true to an extent, but not as much as GURPS makes it. 

The trade-off is a lower DR increase relative to RAW, but also just slightly lower raw penetration (which takes the edge off the larger wound modifiers when not using the granular, limited nature of the pi-/pi/pi+/pi++ scale.
For games, the RAW is, without a doubt, easier. The math-heavy version makes for better comparisons where The Reloading Press is concerned. 

The Reloading Press is an at-least-weekly feature here on Gaming Ballistic for 2016. Each week it looks at some interesting real-world cartridges and presents them with hopefully-useful information in GURPS Format.

.45 ACP / 11.43 x 23mm

The .45 ACP was designed and adopted between 1910 and achieved “final” approval in 1911, when mated with the winner of the platform competition, the now-legendary Colt M1911. Adopted as a result of reported failures to incapacitate the enemy in the Phillipine-American War (the Moro Rebellion) from both the .38 Long Colt and the .30-40 Krag. A bigger bullet with a bigger punch was requested, and this cartridge was modified from a .41-caliber cartridge then under current development by Colt and Browning. 

The basic inputs will be driven from the classic load – the 230gr full metal jacket round that formed the basic projectile more than a century ago. Fired from a 5″ barrel at 250fps, this is in many ways the standard against which all other bullets are compared – if that standard isn’t the 9mm. And if it is, the proponents of the .45ACP are willing to fight them about it.
Ballistic’s Calculator Inputs

Basic inputs for the calculator are as follows, selecting 127mm for the (test) barrel length.

INPUT
.45 ACP
Chamber Pressure 18575 psi
Barrel bore 11.43 mm
Case Length 23 mm
Chamber Bore 11.43 mm
Barrel length 127 mm
Bullet Mass 230 grains
Aspect Ratio 1.5 L/Bore
Burn length 5.5 mm
Projectile Caliber 11.43 mm
Total Accelerated Mass 230 grains
Expansion Ratio 1.7 expansion
Output Stats

The classic cartridge is the original one: the 230gr load which earns the standard GURPS stats of 2d pi+ when fired from the 5″ barrel of the Colt M1911. You can see that the half-damage range is healthy, and that barrel length starts to be substantial in order to eke out more energy from the round.

Notes
  • The velocity is at the muzzle. The velocity with a 5″ (127mm) test barrel is tuned to match real-world data at 830 fps with a 230gr FMJ bullet. This is not the highest energy .45 available, but it’s the standard. 
  • The 230gr bullets have a straight-up pi+ modifier (AP modifier of 1.5) in my model; 185gr are 1.43 and 200gr is 1.46. So pi+ is the rule of the day
Once you get past a 15″ barrel, you’re not helping yourself. At all. So in effect there are three practical barrel lengths for GURPS: 3.2 to 5″ are all in the 2d range. SMG barrels of up to 11″ will get 2d+1. And then carbine-length barrels of 16-18″ will do 3d-1. The intermediate 11-15″ range, while interesting from a GURPS perspective, seems to be a bit of a no-man’s land.

The default original cartridge was a full-metal jacket round. The modern tendency for self-defense pistols tends to be Jacketed Hollow Point, or JHP. These can have some impressive expanded diameters . . . but not that much more than the .40S&W, which makes it a non-issue to trade higher magazine capacity for expanded diameter when dealing with modern rounds.

Not that a 0.7″ to 0.75″ expanded diameter is chicken feed, and the highest expanding load is larger than that of the highest .40 . . . but only by 0.03″.

Alternate Loads

The load chosen for the original was the original. But there are some interesting and impressive hollow-point loads. 

From a GURPS perspective, though . . . the best you can get from a hollow point is pi++. Now, that’s impressive, but you don’t need that much of an expanded diameter to get there, so the really high expansions, while great (perhaps) in the real world, don”t buy you much. From that perspective, the “ultimate” JHP is going to be the highest energy load you can buy that ekes out the full pi++ when expanded. That’s only about 0.59″ with the 200 and 230gr bullets, and 0.60 for the 185gr. All of that means that the bullets on the list below all qualify for a “good” GURPS JHP.

Of the list below, the fastest 230gr load is 908  fps, the fastest 200gr is 982, and the fastest 185gr is 1019. These produce (including proper expansion multiples):

  • 230gr at 908 fps: 2d pi++
  • 200gr at 982 fps: 2d pi++
  • 185gr at 1019 fps: 2dpi++

Recall my model accounts for the JHP not with an armor divisor (in this case a multiplier), but a damage reduction for raw penetration. This basically means that any shooter worth their salt will carry JHP rounds at the full 2d out of a 5″ barrel, and they basically all perform close enough to the same that you don’t need to specify which one you’re using.

Not too many people seem to make high-energy FMJ rounds that aren’t mostly less than 100 grains, so cataloging them isn’t worthwhile. 

Platforms


M1991

The number of .45ACP handguns is vast, vast, vast, but of course you have to start with the actual Colt .45 ACP, now updated as the Colt M1991. This venerable design is also built by a large number of custom pistol shops, such as Kimber, who adds plenty of quality at a reasonable price, and there are other custom shops that do fantastic work (for a high price). Les Baer, Guncrafter Industries, Wilson Combat, Ed Brown, and STI (whose pistols were given to Monster Hunter Owen Pitt as a gift). 

STI Lawman

These tend to be single-stack firearms of the original 7 or 8-round capacity. Larger capacity magazines can be found for those with suitably-larger hands. The Glock 21 held 13 rounds, and other double-stack magazines from 10 to 14 rounds capacity can be had for Sig Sauer, Para-Ordnance, and others. Some of these are available in cut-down versions with shorter barrels for concealability.

In the SMG set, the Kriss makes a unique SMG designed from the ground up to be ridiculously low recoil, and the inevitable H&K SMG – the UMP chambered for .45ACP.

And of course, the original .45 Thompson cannot be left out – both in “gangster” configuration with drum magazines, or the military issue SMG seen in Saving Private Ryan and other movies with stick mags.

The Reloading Press is an at-least-weekly feature here on Gaming Ballistic for 2016. Each week it looks at some interesting real-world cartridges and presents them with hopefully-useful information in GURPS Format.

.40 S&W / 10x22mm S&W

.40 Flat-nose FMJ

The .40S&W was invented after the 9mm bullets that were the standard issue for FBI agents failed to perform as desired during the infamous 1986 Miami shootout. The detals of that are interesting but not pertinent, other than it led to the trial and search for a replacement.

Initially, a 10mm Auto was selected, butt that made for a large-frame pistol and packed a pretty significant whollop. Having personally shot a 10mm, I can attest to this – it’s a handful.

During ballistic tests, it was found that a 10mm 180gr projectile loaded to about 950fps met the criteria for wound channel and penetration depth. That left a lot of air in the 10x25mm (10mmAuto) case, so downsizing it to 10x22mm let the package fit into a 9mm pistol frame. The cartridge debuted in January 1990.

The basic inputs will be driven from a 180gr JHP bullet that matches the standard projectile initially developed for the FBI, selected as a higher energy load that expands well. This provides a healthy energy load . . . but not the most energetic available (which GURPS favors due to conversion factors).

Precis – The Reloading Press weekly feature writes up the .40S&W pistol cartridge.

Ballistic’s Calculator Inputs

Basic inputs for the calculator are as follows, selecting 100mm for the (test) barrel length.

INPUT
.40S&W
Chamber Pressure 34000
Barrel bore 10
Case Length 21
Chamber Bore 10
Barrel length 100
Bullet Mass 180
Aspect Ratio 1.8
Burn length 3.81
Projectile Caliber 10
Total Accelerated Mass 180
Expansion Ratio 1.78
Projectile Load 1

Output Stats

Selected Gel Impact Tracks

This cartridge is designed to be an intermediate in many ways. Intermediate in caliber between 9mm and .45ACP, intermediate in velocity between the 1250fps of the 9mm and the 800fps of the standard .45 ACP.

This one is a 180gr projetile at 995 fps out of a 100mm barrel, which will do even better out of the 5″ full-sized pistol. More on that later, but here’s the chart showing how damage changes with barrel length.

Notes
  • The velocity is at the muzzle. The velocity with a 4″ (100mm) test barrel is tuned to match real-world data at 995 fps with a 180gr JHP bullet. This is not the highest energy .40 available, but it’s pretty good, and within the original FBI specs, so it’s what I chose.
  • Out of a full-sized, 5″ barrel such as the M9 pistol (Beretta M92, or M96 when it’s in .40) there’s no real reason to use a 9mm in GURPS. More on that later.
  • The breakpoint for pi+ in GURPS is currently at 10mm/.40″. You can see that’s a bit generous, as the bullet modeled would be better at closer to +1 per die.
Some more notes on barrel length. There are really two practical lengths for pistols here. The 3-4″ set will deliver 2d+1 damage. The full-sized pistol with a 5″/127mm barrel hits 2d+2. SMG barrels between 6.5 and 11″ long will get 3d-1. After that, carbine-length barrels will eke out 3d.

The JHP with modern design is quite impressive, expanding in this case to 1.77x its starting diameter – and there are commercially-available loads that will expand to a full 2x the starting diameter, though they’re slightly slower. With the model the less-expanding and faster one is better, though. That will do 2d with  calculated 2.4 wound channel modifier. That won’t translate into usable criteria in 4e, as damage tops out at pi++. Still, most .40 weapons will hold 10-13 rounds in a concealable, accurate package that will do 2d pi++, getting the penetration of a 9mm JHP (2d) but the wounding of a .45 ACP JHP (pi++).

Alternate Loads

As noted earlier, the load chosen isn’t the only load, nor is it the “best” from a GURPS conversion standpoint. There are some very impressive loads in JHP (typical self-defense loads, but not military style stuff) in the table below.

The hottest load will do 2d+2 even out of a 4″ barrel, expands to 1.65x (0.66″), and hits the right breakpoints to get 2d+1 pi++ out of a JHP. That’s about as good as you can eke out of a hollow-point round.

Penetration in gelatin of various commercial JHP rounds

In the FMJ category, there are some hot, hot loads out there that require  fully-supported chamber to fire properly. The Glock 22 and 23, for example, were partially supported, and could do nasty things with this ammo.

But if you have the right platform, there are 155gr bullets that zip along at 1300fps (3d), and a very fast 135gr bullet at 1500fps that also does 3d, but is light-weight enough to drop from 1.2 to 1.1, which drops it out of any contention for pi+.

Platforms

Springfield XD(M) with extended mag

There are a huge number of handguns chambered for the .40S&W – it rapidly became one of the most, if not the most, popular chambering for self-defense and law-enforcement weapons – at least recently and in the USA.

Pocket pistols with a 3″ barrel such as the S&W M&P Shield, a few different Kahr pistols, and the 3″ or 3.3″ barrel Springfield XDs will hold 6-7 rounds in single-stack versions, and the XD double-stack holds 9.

The more common 3.8-4″ service pistols blend concealability with 11 rounds in a flush-fit mag, and 15 or 16 in an extended configuration, which is easy on the grip but much less concealable. Glock 22s hold 15 rounds, while Glock 23s are 13.

Springfield XD and Kahr (bottom) 3″ barrels

Full-sized service pistols with 4-5″ barrels still only eke out 2d+1 until you hit the full 5″ barrel, such as in the Beretta M96.

For SMGs, there are of course the usual offerings from Heckler and Koch – the MP5 and UMP. Sig Sauer makes a cool-looking one with an 8″ barrel, which is pretty common for SMG-length weapons.

Finally, carbine-length weapons do exist, with barrel lengths that will tend to be in the 16″ range, but nearly anything in that regime will be identical for stats until one hits too-long barrels in which the bullet will have long-since past the point where the bullet is more slowed by friction than it is accelerated by expanding powder gas.

Sig Sauer SMG

Ultimately, the .40S&W is a nearly magical cartridge for pistols in GURPS. It hits all the breakpoints that GURPS has, allowing for good capacity, good damage, and excellent wounding.

The (0.5) armor divisor that standard rules gives really tamps this down from a “wears any armor and you’re very well proteeted” perspective. If you use the decimal multipliers, though, it occupies a nice space. 20% more injury, about equal penetration, but modern JHP ammunition expands to feasome diameters, easily meriting the pi++ designation given by my system.

The Reloading Press is an at-least-weekly feature here on Gaming Ballistic for 2016. Each week it looks at some interesting real-world cartridges and presents them with hopefully-useful information in GURPS Format.

7.62x35mm AAC Blackout


The 7.62x35mm AAC Blackout was developed to create a .30 caliber cartridge that could be fired reliably from rifles with a particular set of design constraints, mostly owing to the desire to use standard M4/M16 magazines and lower receivers, and to retain the 30-round capacity of standard magazines. Having a weapon that would autofire reliably (the 7.62x39mm does not in M16-shaped magazines) is generally a good thing, and having all that in combination with a more-lethal, more-quiet subsonic projectile was a design goal.

Given the popularity and number of variations that seem to be springing up for this near-wildcat, it would appear to have been somewhat successful. The original cartridge is supposed to have been designed around a military request for short-barreled rifles. The manufacturer took the design public. 

The odds of this replacing the 5.56x45mm as a primary cartridge are probably about zero. Even if the military moved away from the M855 family of rounds, I have to think they’d go for something closer to the 6.8x43mm rather than the .300 BLK. But that’s strictly opinion.


Ballistic’s Calculator Inputs

Basic inputs for the calculator are as follows, selecting 406mm for the (test) barrel length. The difference in mission for the subsonic round means that it can’t really be used for checking consistency, but the lighter-weight bullets (at basically equivalent energy) can.

INPUT – Supersonic
.300 AAC Blackout
Chamber Pressure 53500 psi
Barrel bore 7.62 mm
Case Length 35 mm
Chamber Bore 9.2 mm
Barrel length 406 mm
Bullet Mass 125 grains
Aspect Ratio 3.7 L/Bore
Burn length 10.83 mm
Projectile Caliber 7.62 mm
Total Accelerated Mass 125 grains
Expansion Ratio 2 expansion
Projectile Load 1

The subsonic bullet is very different in both design and performance. It requires different inputs, being less than half the pressure of the supersonic round.

INPUT – Subsonic
.300 AAC Blackout
Chamber Pressure 21000 psi
Barrel bore 7.62 mm
Case Length 35 mm
Chamber Bore 9.2 mm
Barrel length 406 mm
Bullet Mass 220 grains
Aspect Ratio 5.1 L/Bore
Burn length 7.57 mm
Projectile Caliber 7.62 mm
Total Accelerated Mass 220 grains
Expansion Ratio 2 expansion
Projectile Load 1

Output Stats

Again, we’ll need two different charts for each weapon. The subsonic one is (to me) the more interesting, since it actually has a different job than the longer range rounds. I’ll give charts for both.

Supersonic 125gr projectile

The muzzle energy for this load with 406mm of barrel is 1,486 Joules

Subsonic 220gr projectile

The speed of sound is just over 340m/s (which is 1,115 fps). 

Notes
  • The velocity is at the muzzle. The velocity with both cartridges is tuned to the 16″ test barrel.
  • The 125gr bullet is just large enough to make a pi –> pi- transition not relevant. Instead, the real question, given the size of both projectiles, is if it gets a pi+ rating at very short range. Canonically, the answer to this is “no,” but at less than 100 yds from a reasonably-sized barrel, it might be quite nasty. If you like, and want to see players flock to this one, give it pi+ below the range listed, and pi otherwise.
  • No one is going to use this round in a barrel much more than 20″ long (maybe not even that), but the model is within about 60fps for a 78gr projectile from a 610mm barrel . . . so for what it’s worth, it’s accurate enough.
  • The point at which barrel friction slows the projectile more than powder gas pushes it is likely well before 607mm for the subsonic projectile. I suspect a 16″ barrel for 3d is about ideal.
  • Rumor has it that the .300 AAC Blackout at full power will still cycle from a 4.5″ barrel, which is why the table stops there.
Most of the alternate projectiles seem to have roughly the same energy and thus will do more or less the same damage from the test barrel. There’s enough mass in the bullet that getting a JSP to expand to a factor of 2 shouldn’t be a problem. While high-mass, short pistol cartridges tend to convert in the model using a rule that is mostly -1 penetration per die of damage, rifle-shaped fast-cartridges retain penetration better, and are closer to -1 per 2d. That would be about 5d-2.5, call it 5d-3, or 14.5pts. Calling it 4d pi+ is about right. 

The huge aspect ratio and high mass of the 220gr subsonic projectile makes my calculator want to give it 3d pi+ even for the regular FMJ round, and if it expands or tumbles, really wants to give it 2d+1 pi++ for a JHP. That might explain why one keeps hearing that for close-in work with suppressed rifles, certain groups of people who don’t exist definitely don’t want to use this cartridge. Which probably also doesn’t exist. 

In any case, if you’re feeling generous, 2d+1 pi++ for the subsonic JHP or JSP – still -1 per 2d, and bump it up one step from pi to pi+ is good for .300 AAC.

Platforms


There are basically two kinds of platforms for this chambering: AR15-style platforms, and bolt-action tactical or hunting rifles. There are many, many AR-15 style uppers that can be mated to any AR15, M16, or M4 lower – which is the part that the US Government considers the actual gun. 

The venerable and high-quality Remington 700 can be had in .300 AAC Blackout, and the AAC Model 7 can be tricked out with a suppressor. Given the heavy bullet and long 1/2D range, making a subsonic, suppressed bolt-action rifle for the precision delivery role might not be entirely insane. 

The last and most populous category will be a plethora of AR-15 (or M4/M16, as you prefer) lower receivers mounted with a suitable upper. Some of the suppressors that are built to go with this cartridge are very, very impressive, with the AAC SR-7 managing 39dB of noise reduction.

They don’t seem to come cheap. Most are $2,000 or $3,000 for a complete rifle, integrally suppressed or not, and most closer to $3,000 than not.

That being said, going straight to the source a 9″ barrel upper receiver ($1,000) plus the 39 dB suppressor (also about $1,000) will probably deliver 2d pi++ (220gr JHP) from the equivalent of a 16-17″ barrel length (9″ for rifle, 7-8″ suppressor) with impressive (lack of) acoustics.

The Reloading Press is an at-least-weekly feature here on Gaming Ballistic for 2016. Each week it looks at some interesting real-world cartridges and presents them with hopefully-useful information in GURPS Format.

5.7x28mm SS190 by FN

The 5.7x28mm SS190 cartridge was brought to market by FN-Herstal in 1993 (replacing the even lighter, plastic-core/penetrator tip SS90) in response to NATO’s search for a new kind of weapon for vehicle crews and behind-the-line combatants. It was designed to deal with the perception that body armor was going to be more prevalent on the modern battlefield (thus far, not terribly true), and that the somewhat ancient 9mm pistol did not have the killing power and effectiveness that was needed for such troops (that one’s certainly true).

FN really attacked the penetration angle, designing a (relatively) high velocity round that featured a steel penetrator tip.The SS190 will penetrate about 9″ into ballistic gelatin after punching through a Level II vest, which is roughly DR 10 in GURPS. If the 9mm pistol typically is on the order of 18″, that makes the overall penetration around DR 15 or so, giving an idea of it’s penetrative power after the AP is applied. 

Justifiably concerned about wounding power with such a lightweight round (roughly half the weight of the NATO standard 62-gr 5.56x45mm cartridge), the bullet was designed with a steel penetrator tip with an aluminum base. The construction (see pictures below) means that the bullet will break into two pieces (it more or less starts that way) after penetration. Arguments still abound over the wounding power of this round.

There are many loads for the pistol, but the standard one is the SS190 ball round, a 31gr bullet designed to hit 715m/s out of the P90’s 263mm barrel. The key loads are the SS190 (high velocity FMJ “AP” round), the SS195LF (commercial JHP), and the subsonic 56gr SB193. Other loads can be found as well.

Ballistic’s Calculator Inputs

Basic inputs for the calculator are as follows, selecting 127mm for the (test) barrel length.

INPUT
5.7x28mm
Chamber Pressure 45000 psi
Barrel bore 5.7 mm
Case Length 28 mm
Chamber Bore 6.2 mm
Barrel length 263 mm
Bullet Mass 31 grains
Aspect Ratio 2.25 L/Bore
Burn length 4.2 mm
Projectile Caliber 5.7 mm
Total Accelerated Mass 31 grains
Expansion Ratio 1.6 expansion

Output Stats

The one thing you have to know about the various PDW cartridges is that the stats that will come out of my ballistics calculator are almost certain not to match up with High-Tech. The basis for calculation was slightly different.

That being said, one can see that the 5.7x28mm cartridge is definitely pistol-class, even out of long barrels. The bullet well and truly earns a pi- rating, and even a bullet that tumbles and fragments will probably only barely earn a pi rating if the GM is feeling generous. From that perspective, unless the GM is using some sort of calculator or feeling generous, the lower pi- rating of all of the bullets will mitigate towards the highest energy round possible unless the goal is to push it through a suppressor, in which case the heavier, slower, lower energy SB193 will be called for, giving up some penetration in exchange for (relative) silence.

So, here’s the chart:

Notes
  • The velocity is at the muzzle. The velocity with a P90 263mm test barrel is tuned to match real-world data at 715m/s. Out of the 122mm Five-seven pistol, it develops just shy of 600m/s according to my model. 
  • The pi- to pi range is a bit dubious in this case. The bullet’s construction means that fragmentation is all but inevitable, but the low mass of the SS190 round, combined with the low cross section, means that pi- is likely the better figure regardless of range.
The P90 uses a 163mm barrel, which puts the KE-based damage for the cartridge at about 3d-1 using this model (compare with 2d+2 in High-Tech). The trick here is that the High-Tech stats give the basic round the full armor divisor of (2), the only resolution that GURPS can provide. With a more-realistic divisor of 1.25 to 1.5, and looking at the “penetrates about DR 15 ish” above, we can see that a net damage rating of 3d-1 (1.5) pi- would penetrate to about DR 15, but only do about 4-5 points of wounding per shot. This is roughly consistent with the observed performance of the round, though 3d-1 (1.5) pi or 2d+2 (1.5) pi would not be tragic, either, retaining the DR 13-15 penetration observed in body armor testing, but wounding like a 9mm pistol. 

One last thing: I’m dubious about the penetration statistics, though it is hard to argue with data. DR 15 is quite nearly the penetration of a M4 carbine, a cartridge with over 3x the energy and similar cross section. 

The two barrel lengths of import for most uses are the 263mm barrel of the P90, and the 122mm barrel of the Five-seven pistol.

Alternate Loads

As noted earlier, the JHP load likely won’t expand sufficently to mathematically eke out a boost in damage, but for GURPS purposes, a good rule of thumb here will be to subtract two points of penetration (so the pistol becomes 2d (1.5) pi and the PDW is about 2d+1 (1.5) pi ). 

The other important load is the 56gr and 305m/s SB193, designed for subsonic use with suppressors. That is 1d+2 pi-, with no armor divisor. Aim for the head, and fire a lot of bullets.

Platforms


There are basically three classes of platforms – or rather, two concrete weapons, and then another class of “if you want this cartridge, you can . . . “

The Five-seveN pistol is the companion piece to the PDW that formed the basis of the cartridge. It has low recoil, a 20-round capacity, and the long overall length relative to the 9mm and other handgun cartridges means that one needs monster hands to completely enclose the grip. The relatively low damage of the round means that it’s wise to fire more than once, but then, if something’s worth shooting, it’s worth shooting twice. Or more. If you can handle the grip, I suspect that putting bullets through more or less the same hole is the rule of the day.

The design platform for the weapon is the P90 PDW, a compact weapon with an unusual layout and even more unusual magazines. They top-load, and eject through the stock. The overall length and compactness of the weapon make it very handy for entry and close-quarters work. Despite the claims of 200m effective range of the platform, I suspect that nearly all of the work done with this weapon (and it’s found its way into service with numerous SWAT-style teams internationally) is at 50m or less, where penetration is maximized, the odds of getting multiple rounds on target are very high, and the teams can rely on multiple hits and compound wounding tracks to incapacitate.

Both the pistol and PDW can be found in High-Tech.

The final class of platforms are weapons like the AR-57, which is basically a 5.7x28mm upper receiver, complete with top-loading magazines, mounted on an AR15 lower. The magazine in the photograph to the right does not feed rounds, it catches them – it’s hollowed out with the spring and follower removed. Personally, I’d probably try and line such a device with felt or something, so as to minimize the rattle, but one can also just remove the ersatz brass-catcher and let the rounds eject through the mag well. The barrel of this weapon is 16″, perhaps even squeezing out 3d+1 raw damage, but certainly earning 3d. Such uppers seem to retail currently for $700-750.

The Reloading Press is an at-least-weekly feature here on Gaming Ballistic for 2016. Each week it looks at some interesting real-world cartridges and presents them with hopefully-useful information in GURPS Format.

9x19mm Parabellum

The 9x19mm was invented by Luger in 1902. It is perhaps the most widely used pistol cartridge worldwide, and with recent advances in hollow-point ammunition reliability, is poised to reclaim its former spot as the issue cartridge of the FBI over the .40S&W.

There are many loads for the pistol, but the most common seem to be the 115gr, 124gr, and 147gr loads. They are usually available in full metal jacket (FMJ) and various flavors of hollow point. From a GURPS perspective, the most important load is probably the 124gr NATO standard round – an 8 gram bullet fired at 1250 fps from a 5″ barrel – it’s the standard for 2d+2 as well as pi pistol rounds. A reference bullet, so to speak, defined as doing both 9 points of penetration and 9 points of injury.

So we’ll work that one up, and then talk about variations.

Ballistic’s Calculator Inputs

Basic inputs for the calculator are as follows, selecting 127mm for the (test) barrel length.

INPUT
  124gr 9x19mm  
Chamber Pressure 32900 psi
Barrel bore 9 mm
Case Length 19 mm
Chamber Bore 9 mm
Barrel length 127 mm
Bullet Mass 124 grains
Aspect Ratio 1.85 L/Bore
Burn length 8 mm
Projectile Caliber 9 mm
Total Accelerated Mass 124 grains
Expansion Ratio 1.66 expansion
Projectile Load 1
Output Stats

The pistol cartridge is relatively high power as far as pistols are concerned – much more so than the .45 ACP that it was supposed to replace (and from a service perspective, largely did replace). It develops a considerable velocity in a short barrel, and the lowest penetration predicted by the model is on the order of 2d out of just over a 1.5″ barrel – not that anyone uses one that short. Even derringers come with a 2.5″ barrel, mostly!
So, here’s the chart:

Notes
  • The velocity is at the muzzle. The velocity with a 5″ test barrel is tuned to match real-world data at 1250fps, for NATO standard ammo. This is not the highest energy 9mm available, but it is the standard GURPS 2d+2 pi bullet, so it’s what I chose. 
  • 1250 fps is pretty good for a 9mm load, though – not that you can’t get more, but in self-defense loads (JHP), the fastest 124gr tested at this site was slower than the standard FMJ NATO load.
  • There is no pi to pi- range; this bullet does not gain appreciable wounding by tumbling.
Some more notes on barrel length. You can see that it will penetrate as well as a .45 ACP with derringer-length barrels. At the more standard 2.5″ or higher, it’s at least 2d+1, and in the “service pistol” barrel length from 4″ to 5″, it’s all 2d+2.

Now, for SMGs you can get longer barrels – but not as long as you might think. The MP5K has only a 4.5″ barrel (2d+2) but can hold a lot of bullets and fires them quickly. The more robust MP5 is 225mm for the longest barrel, which only ekes out 3d-1. To get to the full 3d you’ll need/want a 9.5″ barrel, but you can’t get to 3d+1 until you’re over 450mm. Even the Beretta Cx4 Storm is only 422mm – most carbines seem to like to come in 16″ barrels or smaller (3d), but the Citadel M1 does come with an 18″ barrel that should deliver about 3d+1. Of course, if you are toting a 35″ weapon around, you can do a lot better than that for damage, ammo weight, etc with a 5.56x45mm carbine or even a full-size rifle in a bullpup. The reason you do this (carbine in 9mm) is for Accuracy, not damage.

Alternate Loads


As noted earlier, the more common loads than the military one will be hollow points. That being said, there are slightly hotter 124gr FMJ loads, the hottest I could find only being 1310fps, which my model gives as being achieved at about 36,200psi input. That gives 9.8 points of damage, which is enough to eke out 3d-1 pi.

Alternate loads tend to be alternate weights, with a lot of 115gr stuff being available as very high velocity rounds, especially from SMGs, and 147gr heavy bullets from pistols, both of which are available in JHP. The heavier bullets will tend subsonic, which makes them excellent for platforms like the MP5SD6 – an integrally suppressed weapon.

Some of the best JHP will expand to as much as 0.6 to 0.7″ in diameter, which is roughly double what the starting diameter is. That’s very good, and more typical of JSP rifle rounds – which have a lot more body to work with.

That means a proper JHP round really earns it’s pi+ rating. The GURPS rules give JHP ammo a (0.5) armor divisor. The more accurate way to do it is to subtract 1 point of penetration per die. Lo and behold, this makes the best 9mm hollow point from the prior web page (1170fps and 0.66″ expansion, the Golden Saber +P loads) provide 2d pi+, which is the same penetration and injury as a .45 ACP, but with a heck of a lot more shots per magazine and less recoil. 

Platforms

There are almost too many to count. I’ll ping in a few important ones.

Pocket pistols with a 2.5″ barrel that would include derringers and small concelable pistols like the Kahr and other 9mm models. These will often hold fewer than 10 rounds.

Concealed carry pistols with a 3-3.5″ barrel that are “commander-sized,” which means small and easy to carry, but likely double-stack weapons that will hold over a dozen shots, perhaps closer to 15.

Full-sized service pistols with 4-5″ barrels. These will hold 15-18 shots in the magazine.

SMGs and Carbines with 9″ to as high as 16″ barrels. Nearly all will do about 3d-1 or 3d pi damage, and with the right hollow-point round will deliver 2d+2 pi+, which is a good reason to carry one (still not as good a reason as to carry a carbine with an assault rifle chambering for many reasons).

As noted above, subsonic 9mm is good for suppressed weapons, the most famous of which is probably the MP5SD series.

The Reloading Press is an at-least-weekly feature here on Gaming Ballistic for 2016. Each week it looks at some interesting real-world cartridges and presents them with hopefully-useful information in GURPS Format.

6.8x43mm SPC

The 6.8x43mm SPC cartridge was introduced as an attempt to increase the lethality of the M16 and (especially) M4 pattern rifles. The cartridge is more-or-less designed to fit into the same magazine length as the 5.56x45mm NATO standard bullet (but it’s not true that they use the same magazines – they don’t), and the lower receiver of the AR15/M4/M16 platform can be used unmodified with the new cartridge. The bolt, chamber, and barrel of course must change, and that can be done with an upper receiver swapout.

Whether or not this was the true design goal, one outcome of the design process that led to the 6.8x43mm is that the test velocity of the barrel is achieved with a 16″ barrel, rather than the 20″ standard for the 5.56x45mm. That means that the M4, with its 14.5″ standard barrel, is much closer in barrel length to the optimal barrel the cartridge is designed around.

Ballistic’s Calculator Inputs


Basic inputs for the calculator are as follows, selecting 406mm for the (test) barrel length.

INPUT
6.8x43mm SPC
Chamber Pressure 54000 psi
Barrel bore 6.8 mm
Case Length 43 mm
Chamber Bore 10.7 mm
Barrel length 406 mm
Bullet Mass 115 grains
Aspect Ratio 3.6 L/Bore
Burn length 21.3 mm
Projectile Caliber 6.8 mm
Total Accelerated Mass 115 grains
Expansion Ratio 2 expansion
Projectile Load 1

Output Stats

The rifle develops appreciable damage at near pistol-length barrels, at least within the assumptions of the calculator. It would equal the injury of a .45 ACP even at pi- ratings in a barrel the size of a long revolver. Even so, calling it “pi-” does it little justice. It would earn a wound channel modifier of 0.7 if the scale were left open to any number, compared to the 0.5 of the 5.56x45mm, the 1.0 of a 9mm, and a 1.2 of a 0.40 S&W.
So, here’s the chart:
Notes
  • The velocity is at the muzzle. The velocity with a 16″ test barrel is tuned to match real-world data at 2575 fps, the highest energy load listed on the Wiki page. I do this because GURPS damage is based on kinetic energy, so no GURPS PC worth their salt will choose anything less than the highest energy if pure penetration/lethality is at issue. If you’re doing supppressed subsonic shooting, that changes.
  • The pi to pi- range is where the damage drops from piercing to small piercing. For very short barrels (smaller than 177mm in my model), the bullet is slow enough that it will not yaw and fragment, and so it’s only good for pi- rather than pi. This is defined as 600m/s in my model, which is somewhat arbitrary.
  • It’s possible that the damage (penetration, really) is perhaps 10% high. That would still give a 20″ barrel about 6d-1, and a 14.5″ barrel 18 points of penetration, or a full 5d out of an M4 platform.
At any useful barrel length for a rifle cartridge, that is, about 9″ and higher (and that’s a darn short rifle), there is some appreciable range at which it will do its full pi damage type. It is an intermediate between the 5.56 and 7.62 NATO offererings in almost every way:
  • Half the diameter of the two rounds would be 6.59mm
  • Half the bullet weight between the 62gr and 168gr standard marksman’s bullets for each platform is 115grains, which is where the standard bullet comes in
  • The standard AR-15 length magazine holds 25 rounds of 6.8mm SPC; the AR platform magazines typically hold 30, while the 7.62×51 hold 20.
  • The 7.62 is about 3400 Joules, the 5.56 about 1760J. Average that to get about 2,550J, where the actual round comes in at about 2,300J.
For GURPS gunners, it’s a very good cartridge. 6d out of a 16.5″ barrel makes for a one-shot death check against Joe Average, bringing him from 10 HP to -11 HP in one torso hit. Against the vitals, 21 turns into 63, enough for a one-shot instant auto-kill. Highly efficient. The Rcl for these weapons is typically 2, so it’s no worse than the M4 or M16 it replaces, and better than the full-size battle rifles. The 1/2D range of 530yds is 30% higher than the 5.56x45mm.
Regardless of the real-world, it’s a fine, fine cartridge in GURPS.
Not everyone feels the same way about the cartridge in the real world as it stacks up vs. the modern versions of the 5.56x45mm, the Mk262 77gr long-range cartridge. A data-intensive comparison can be found here.
Platforms

You need a purpose-built upper receiver (or at least a barrel, chamber, and bolt change) to shoot this cartridge. Some rifles and uppers can be found below.

  • The Barrett REC7 is the only 6.8 SPC rifle statted up for GURPS, found (of course) in GURPS Tactical Shooting. For a list price of $2,800, one can be yours.
  • I would love to get my hands on a Desert Tech MDR in 6.8 SPC, but they’re not out yet. They’re also supposed to cost between $2,000 and $3,000. But it’s a bullpup, so mrowr.
  • Stag arms makes a piston-driven platform in 6.8x43SPC that’ll run the buyer about $1,100, but you need to have a lower receiver to put it on (about $300, and that’s the part that counts as a “firearm.”
  • LWRCI went the entire nine yards, redesigning the magazine well and contractiing with Magpul to make the only polymer-case magazines for this cartridge. The rifle itself is about $2,200 complete, and each magazine costs a darn-reasonable $25.
  • The magazines for these rifles are quite finicky in my experience. Of the four 25-round steel magazines I own, two will not feed reliably. Barrett and Magpul make good ones, for $50 and $25, respectively.
  • You can find some of the above, and many others, in this article. They’re all probably very expensive, though – this round never caught on as much as marketing hoped it would!

There’s an interesting thread with some strong opinions being given over on the SJG forums working out the details, pros, and cons of a house rule where you double HP (and DR). ST-based damage would be left alone, in order to restrict the muscle-powered weapon damage to penetration values more in line with firearms.

Given the wound probabilities (really, not necessarily that bad with modern medicine unless certain vital bits are hit – you’re going to be messed up but a fairly low probability of dying) the fix for firearms under this system would be to just give them all an armor divisor of (2).

So the general penetration formula remains the same. Wound modifiers would probably have to stack with hit location (so pi+ to the brain is x1.5 x4 = x6, while the vitals x3 and pi+ would be x4.5, rounded up to x5) in order to make up for the loss in low-grade lethality. Does that mean impaling goes from x2 to x4, and cut from x1.5 to x3? Probably not – those stay the way they are.

So, that’s the theory, and the pros and cons and dos and don’ts are pushing 90 posts, so it’s contentious in many ways.

Double HP and Cubic ST individual concepts

Still, I talked about this before. Rescaling GURPS HP had me musing about the pros and cons of using double the HP score, and its impact on resolution for things like body mass. My parting shot really only noted that the increased resolution that double ST/HP provided was pretty friendly.

However, even right before that, I’d noted that yet another concept, posited by forum user Wavefunction, which was figuring Basic Lift off of the cube of ST, rather than the “quadratic lift” basis of the current Fourth Edition rules (and compared again to the linear ST of the Third Edition and earlier rules).

The “good news” about that was that if you restricted ST to the current equivalent to a ST 20 (Basic Lift 80 lbs), that dropped the Cubic ST equivalent score to ST 16. At that point, you punched at 1d+1 (as much penetration as a .22 LR bullet), and swung for 2d+2 (as much penetration as a 9mm pistol).

Now, one should probably give significant armor multipliers to such blows – at least (0.5) if not (0.33) for fists and such – but at least the upper end didn’t have you swinging for enough penetration to make a 10mm bullet look like a poor trade.

Of course, that’s realism. As I was discussing this sort of thing tangentially with +Christopher R. Rice as I made a Captain America-type superhero at nearly 900 points – the issue with punching folks for a living isn’t that hitting them is more effective than guns. It’s that, in a world of guns, you usually can’t survive closing to fisticuff distance. From that perspective, both bows and fists/feet need the damage boost to make up for the fact that they just suck compared to ye olde .40 S&W. That’s an explicitly genre-balance argument, not a realism one, but nonetheless, the terrain is clear.

Let’s all eat Reese’s Peanut Butter Cups

What I did not do, and probably should have, is combine the two concepts. Ideally, this would give the increased resolution from doubling HP, the matching of ST and body mass for cubic ST and the cubic base of HP. We’ll need to tweak to get the damage scaling, but that’s tractable.

So, here we go. The Big Chart.

This one is scaled in HP, with the assumption that ST = HP, since my original thought was that you’re basically buying body mass, and then can tweak your ST by up to +4 on the upper end, Why that? We’ll get there.

So let’s look at the table for a bit. The green band is the starting HP for GURPS with no adjustment to how HP are calculated from body mass other than doubling. That is, take the cube root of weight (so 125 lbs –> 5) and multiply by 4. Unliving/Machine and Homogenous/Diffuse (p. B557) would thus be x8 and x16 times the cube root of object weight.

The shift to cubic ST means that (as you can see from the table) the 6xBL threshold and the actual object weight scale well, so a ST 50/HP 50 critter should move in the same manner as a ST 5/HP5 creature. That makes it easier to pick ST and HP values for oddball monsters, I think.

This probably means we can use the Size and Speed/Range Table for a comparison of muscle power to mass (ST to HP) and get pretty good “you can launch that object so far” values, which would make it relatively easy to accommodate ST in the jumping formula, as well as velocities and damages for thrown objects and weapons. Good stuff, and rationalizing all of that in one rule is worthwhile.

Anyway, the green band is the same default basis as the current rules, except HP are doubled. Basic Lift is left at 20 lbs.

Now, when looking at the upper end of the scale, what used to be ST 20 (and Basic Lift of 80 lbs), the scaling change means that that value falls to ST 32 on the new scale,with a Basic Lift of 82 lbs.

This means that unlike the range of 10-16 we got with just Cubic ST with no change in HP, players can easily make finer resolution distinctions in ST scores within the normal range. Given that 6-8xBL is probably a good proxy for world-record bench presses, anywhere from ST 34 to ST 36 represents a human maximum. I’ve previously pegged squats as around 1.5x that value, so 9-10xBL works there, and again, dead-lift and squat of around 800-1,000 lbs tags well there. On the “low” end, it’s not crazy-town to have a 160-lb person pressing 240-lbs, so having HP 22 (166 lbs) be as strong as ST 26 (6xBL of 265 lbs) doesn’t strain credibility.
What about bows? Using the Deadly Spring’s pegging of maximum bow draw as about 2.5xBL, and allowing an extra +4 to ST with leveled Strongbow perks and perhaps another +4 for Arm ST with Special Exercises, our HP 22/ST 22 person could wind up with ST 30 for the purposes of drawing a bow – that would be a 68-lb. basic lift, or a draw weight of 170 lbs. That’s a proper adventuring-strength bow! It’s also on the upper end of the Mary Rose reconstructions, which hit as much as about 185#. Mark Stretton, one of the more famous heavyweight longbow guys (but not the only one) masses a lot more than 165 lbs., and he pulls a 200# bow (he may pull more; I’ve seen the video of the 200# one). I’ve seen a much more svelte guy draw back a 170# bow and make it look easy, so I’m not scared of the results here.

Whither Damage?

The big question here is what happens to damage? Well, with the forces in pounds, energy for penetration should probably go as the square root of basic lift. That will scale it on the same trajectory as firearms, with is one of the goals of such projects.

Where do we put 1d, though? I don’t have much of a problem with old ST 14 (with 39 lbs basic lift) having a 1d thrust score. If we assume that stays constant with a BL of 39, that means 1d thrust happens for us at ST 25. If swing gives about double the force of thrust, that’s about 40% more damage.

That’s about +3 per 2d (which is messy), but a +1 or +2 per die is less so. Let’s give it +2 per die, which is still about a 40% reduction in both the absolute value of damage as well as cutting down the scaling quite a bit. So: ST 25 is 1d thrust and 1d+2 swing. Note that if you give thrusts with an appropriately-constructed weapon an AD of (2), this results in the thrust being better able to penetrate armor than the swing.

What about default and maximum ST?

ST 20, our new default, clocks in at 2.5 points of damage, which is exactly 1d-1. That’s actually a one-point boost over ST 10 using the table on p. B16. For swing, it should be about 3.9 points, which is between 1d and 1d+1, so the “2 per die” thing is a bit generous, but not horrible, giving 1d-1 for thrust and 1d+1 for swing.

At the upper end with ST 32, scaling as the square root of Basic Lift, we get 5 points of thrust penetration and about 7.9 points for swing. That’s between 1d+2 and 2d-2 for thrust, and about 2d+1 for swing, which means the 1d+1 would be a better fit for thrust.

That very much reduces the range of damage between average and what’s considered the normal human maximum. That’s going to make things cheaper, since the highest proportion of the cost of ST is Striking ST.

Cost Breakdown

ST is one of the only attributes to break neatly and easily into its component costs. GURPS values striking at 5 pts per level, lifting at 3 points per level, and HP at 2 points each. That means you pay about 10 points per point of thrust damage.
Applying similar scaling to this new scheme, we get:
  • HP are straight-forwardly 1 point per HP. Going from ST 20 to ST 32 should be 12 points.
  • Striking ST thrust damage goes from 2.5 points to 5 points in the new scaling. That should be 25 points if the cost per point of damage stays the same. We’ll assume that it does, since one of the purposes of the re-scale is to lower the ability to deal penetration.
  • Finally, the move from Basic Lift 20 lbs to Basic Lift 80 lbs costs 30 points in the current rules. We can make that same move in Basic Lift cost the same amount. So Lifting ST 20 to Lifting ST 32 costs 30 points.
Total it up, and going from ST/HP 20 to ST/HP 32 should be 12+25+30 = 67 points for 12 ST/HP. We’ll call it 5 points per level, which pleases pentaphilia as well as acknowledging that damage especially isn’t worth what it used to be.

The breakdown is 1 point per HP, 2 points per point of Striking ST, and 2 points per point of Lifting ST. That again works: Lifting goes up faster than it used to so it’s worth more; damage is less valuable because it scales slower and flatter, so it’s worth less.

What about new ST/HP 100? That’s going from ST 20 to ST 100, or +80ST, which will cost 400 points. You’re lifting more than a ton with Basic Lift alone, but your damage is only about 8d thrust, and 8d+16–> 12d+2 swing.

Parting Shot

A lot of the games in which I play lower the cost of ST anyway. 5 points/level or even 7 points/level seems like a common value. The trade-up with the higher resolution but increased scaling for lift provides a bunch of small steps with which to differentiate between characters by virtue of physical power.

The real benefit here, to my mind, is the unification of ST and HP values so that they’re explicitly tied to mass and movement capability. When you can say “if your ST and HP match, you’ll move like a human in terms of acceleration, jumping, climbing, etc.”

There will be things that go wrong, of course. The wound thresholds for when one makes death checks might need adjustment – perhaps halving them on the negative end, or just using the usual breakpoints from the Size and Speed/Range Table.

So instead of every -1xHP something bad happens for your life, it might happen at -HP, -1.5HP, -2xHP, -3xHP, -5xHP. Auto-death would thus be at -3xHP, and unrecoverable mess at -5xHP. Note due to doubling that’s about where they used to be.

Characters will be able to take a lot more gunshots to the torso before expiring. One shot to the generic torso with a 5d rifle will leave you reeling but not in danger of KO or death if you have more than 18 HP. One shot with a generic 7d rifle will threaten an average person, but 25 HP and higher (more than about 240 lbs body weight) and you can take one shot.

To the vitals, those hits turn into 51 HP and 75 HP (more or less) respectively, putting Joe Average to -30 (-1.5xHP) and -55 (more than -2xHP but not -3xHP) respectively. So you’re looking at death checks there.

For pistols, the usual 10 HP  per shot (2d–>7 pts x 1.5 for pi+, or 9pts for 2d+2 pi) means that to the torso, you can soak up two shots and still be reeling but in no danger of immediate loss of consciousness. To the vitals, again, we wind up with about 30 HP per hit, so a shot to the Vitals puts you at one death check. So shot placement matters more in this system, which is to the good.

It’s cheaper to get to maximum Basic Lift for regular humans of 80 lbs. That’s 12 points of additional ST, for 60 points, instead of the 100 pts it costs under RAW. Again, that’s not tragic.

Tying HP and ST more closely together is a thing for me, so that doesn’t bother me. Lacking GM permission or superheroic genre, the “you may increase ST to as much as 4 points higher than your mass-based HP” means you need to be about 350-lbs to hit 80-lbs basic lift, which means you’re probably capable of pressing nearly 500lbs with arms alone, and dead-lifting or moving with your back something like 800-900 lbs. Having the mass of a heavy athlete in order to do feats of strength that heavy athletes do? Win – for me.

An equivalence of HP and weight would make a lot of in-game calculations easier, since you could look at strength-to-weight ratios easily by looking at shifts on the size and speed/range table – it’s logarithmic in nature, so looking at differences in the modifiers on the table means you’re doing ratios. Again, this unifies and simplifies the normally complex.

The down side here is that the ability to do penetration-based damage, with thrust or swing, has been utterly and totally nerfed. If a plate harness has just gone to DR 12 where it used to be DR 6, you’re totally immune to blows of less than 2d. For some, this is the reason for doing all this. For others, such as anyone playing Dungeon Fantasy, it may well be a “and that’s why I’m not ever going to do this. Nope.” death-knell.

Oh, and a word about bows and arrows. The switch to damage as sqrt(lifting) probably means that calculations using The Deadly Spring can be based right off of ST. The ST 16 yew longbow (128 lbs draw) does 1d+1 “realistic” damage. That requires a Basic Lift of 51 lbs, which is ST 28 on the new, revised scale. Thrust damage there is 4.1 points, or between 1d and 1d+1. Cinematic damage for this bow was 1d+3. So if a longbow did thr+1 in a realistic campaign or thr+3 in a cinematic one, that would probably simplify things quite a bit.

Crossbows? Heh. The medieval crossbow from The Deadly Spring requires a Basic Lift of 90-95 lbs to span by hand. That’s ST 33 in the new system, for thrust of 1d+2. However, the actual damage of this crossbow is 1d-1, because even though it’s got a draw strength of 740 pounds, the efficiency with which it launches the bolt is low. So crossbows do thr-3 (2) imp damage on the realistic scale, and thr-1 (2) imp for a cinematic one. That two-point differential seems to hold for both types of launcher.

So for bows, you no longer need math – just the table and a ST lookup – to get either realistic or cinematic bow penetration. Injury – which can be quite severe – will be taken care of with the stacking of x2 for imp with x3 for vitals – an arrow to the heart for 1d+1 is no joke, turning into 6d+6 injury, for 27 HP on the average, enough to force KO checks immediately and depending on how harsh one is for bleeding, death by blood loss soon after.

Again – I’m sure there are issue here, but by math alone, it’s not fatally flawed. I’d definitely be interested in seeing this in play for a few sessions.

I have no idea why I did this. But I was thinking, probably because of my comments in my firearms-related Violent Resolution column.

But  . . . I wondered to myself if there was a way to turn some sort of real-world number into D&D damage output.

I know, I know. Why would I ever do such a thing? I had noted (complained, really) that a 9mm was 2d6, and the mighty .50BMG was but 2d12.

So . . . I whipped out solver, and it turns out if you use the energy of the bullet, and only the energy of the bullet, if you use 4 * Log (Base 5) Energy you get a number that might just equate to the maximum damage you can roll on the dice. It compresses the scale even further than the usual result, but it’s not insane.

Examples?

Cartridge Name D&D Damage? Roughly
.22LR 12 2d6
.380 ACP 13 2d6+1
4.6x30mm PDW 15 2d6+3
.45 ACP 15 2d6+3
5.7x28mm 16 2d8
.40S&W 16 2d8
124gr 9x19mm 16 2d8
.45GAP 16 2d8
180gr 10mm Auto 16 2d8
5.45x39mm 18 2d8+2
240gr .44M 18 2d8+2
.50 AE 19 2d8+3
M855 5.56x45mm 19 2d8+3
7.62x39mm 19 2d8+3
6.8x43mm SPC 19 2d8+3
12 Gauge Shotgun Slug 20 2d10
150gr NATO 7.62x51mm 20 2d10
.500 S&W 20 2d10
.30-06 21 2d10+1
.300 Win Mag 21 2d10+1
.338 Lapua Magnum 22 2d10+2
.50 BMG 24 2d12
14.5x114mm KPV 26 2d12+2
120mm M829-A1 39 6d6+3
16″ Naval gun 49 8d6+1
A shortbow or longbow with a good DEX will get you 1d6+4 or 1d8+4, which are 10 and 12 max damage . . .basically a longbow has the same max as a 2d6, which energetically works out fairly well, since powerful bows deliver on the order of 100-200J. So that’s not crazy-town.
Now, this is totally based on energy, and that means the big, slow bullets are worse than small fast ones. Fine – acknowledged it’s not perfect, but it’s a scale that actually fits reasonably well with d20 Modern and can be extrapolated to other weapons.

Show the Work

How did I do it?

I tried to make a .22LR 8 points (2d4), a 9mm 12 points (2d6), and a .50BMG 24 points. I used a formula to set a quantity of D = A * logB(Energy). I squared the difference and normalized it to the target squared . . . so (D-T)^2 / T^2. I also weighted the results, so the .22LR got 1000x the figured sum, the 9mm got 4000x, and the BMG got 9000x. That was to force Solver (in Excel) to give more weight to making the .50BMG 2d12 or 24 points. The energies I used were 130J for the .22LR, 585J for the 9mm, and 14,700 for the .50BMG, which assumes a man-portable 32″ barrel instead of the 43″ bbl on the machinegun (which is about 16,000J).

Solver gave an exact figure of A = 3.88 and B of 5.1. But setting A=4 and B= 5 is actually better at fitting the BMG, and puts the .22LR at the 2d6 value above. Given the energy involved, that’s probably as good as the d20 modern values.

When converting max damage to dice, I always use the largest dice I can, but don’t allow subtraction. So 19 points isn’t 2d10-1, but rather 2d8+3. That’s a quirk of mine. You can certainly convert any way you like, and 39 points could be 4d8+5, 4d10-1, or 3d12+3 easily enough. Heck, have at it and make it 9d4+3, and the 16″ Naval Gun 12d4+1 to keep the minimum damage high.

Note that the Naval Gun is just the kinetic energy. I haven’t yet figured out how to rate the explosion of 150 lbs. of high explosive inside about 2,000lbs of metal.

Bah! The Damages are Too High!

A comment on G+ noted that 3e humans only have 4 HP, which is a fair point. If you wanted purposefully lower numbers, then here are some nudges/hacks, as well as my line of thought.

I based them off of d20 Modern’s list, where a 9mm was 2d6 and a .50BMG was 2d12. The math forced the 9mm to 2d8 and put the .22LR, which I tried to make about 2d4, into 2d6.

In 5e, at least, a 1st level fighter is going to start with at least 10 HP, and you get a DEX bonus to the 1d6 or 1d8 base damage of a short or longbow, respectively. So from that perspective, 2d6 (ish) or 2d8 for a pistol is the equivalent, on the average of 1d6+3.5 and 1d8+4.5 for damage, neither of which is out of line for d20 Modern or 5e, at least.

If you lower the values to make them work for low level characters, you have the opposite problem – a high level fighter can shrug off a burst of .50BMG unless you invoke the harshest of harsh wounds rule where if you take more HP than your CON, you save or die (that’s a suggested threshold – the harshest one – from the d20 Modern SRD).

If you force the .22LR down closer to a shortbow, the formula becomes something like 2*log(base4) Energy. That makes a .22LR 1d6+1, a 9mm about 1d8+1, a 5.56mm 1d10+1, 7.62mmNATO 1d12, and a .50BMG 1d12+2.

This gives fewer categories of damage

  • 1d6+1 for .22LR
  • 1d8 for .380 ACP
  • 1d8+1 for PDW rounds and all normal military pistols (.45 ACP, 9mm, 10mm, .40S&W)
  • 1d10 for magnum pistols (.357M, .44M) and lower-powered assault rifles (4.73x33mmCLS, 5.45x39mm)
  • 1d10+1 for standard military assault rifles (5.56, 6.8SPC, 7.62x39mm, 6.5 Grendel)
  • 1d12 for battle rifles and sniper rifles from .308 to .338 Win Mag
  • 1d12+1 for .338 Lapua or .416 Rigby
  • 1d12+2 for .50BMG