The concept of Trained ST features prominently in GURPS Martial Arts: Technical Grappling. It’s one of the core rules concepts, and is designed to represent my personal observations that being a really, really good grappler can substitute somewhat for being really strong . . . but if you can be really good and really strong, yeah . . . do that.
The core concept – and one that appeared in print first in The Last Gasp, even though it was first written a rather long time ago in the TG manuscript – is that the more points you spend on a skill, the better you can apply your ST with that skill.
In fact, not just “better applied,” but “actually stronger.”
In short, this is one way of getting sport-specific training, so to speak, into your games.
So, we did it for grappling, and basically extended the progression you see in (for example) Wrestling, where you get +1 to ST at a skill level of DX+2, and +2 to ST at DX+2 upwards a ways. As far as DX+10.
Interesting. Well, don’t Karate and Brawling have similar bonuses?
Yes, yes they do.
So why didn’t I take the next step? Broaden the concept to include weapons skills, as well as unarmed combat. The door was open, right? All I had to do is step through it.
Well, first and foremost, I wasn’t rewriting the GURPS Basic Set. Sure, +Sean Punch let me radically muck with something by allowing me to implement Control Points – more on those later – but the basic model of the rest of the rules wasn’t jostled much. You could drop the new rules on to existing campaigns and not break anything – but if you started doing crazy stuff with weapons, you’re really mucking about with existing characters. That could be seriously non-fun.
Could it be done, though? Could one take the existing relationships between damage and ST and make it work better?
I’m sure you could. One way to do it would be to, well, just do it. But do it in a less-nasty way. If you’re in to rescaling melee damage, Then large bonuses, or percentage multipliers, on ST wouldn’t be that ugly. If at ST 12 you’re doing 1.2d (about 1d+1) swing and 0.6d (1d/2) thrust, then boosting ST by 50% when you hit DX+10 skill would give you effective Trained ST 18 . . . or 1.8d swing and 0.9d thrust (about 2d-2 and 1d respectively/more-or-less). That’s just not going to break anything.
In order to not really get melee weapons damage out of hand by just boosting it all, you’d probably want to take the thrust and swing damage table, and make an assumption such as “this is the damage you get when you get to DX+2 skill. If you have less skill than this, you don’t do as much damage.
You’d then lower the damage for lower skills, from DX+1 down to defaults on the order of DX-6. Well, you’d not lower the damage, you’d lower your (un)Trained ST with the weapon. It wouldn’t change, perhaps, the ST you use when looking at the minimum ST of the weapon (though it could), but it would give you a darn good reason to train.
What might that table look like?
If you’re into scaling (and you should be), substitute a 10% increment (rounding down to lower ST) instead of a -1. So if you were normally ST 12 with a broadsword, but only had a point in the skill, you’d be operating at either ST 9 (-3 to ST) or -30% to ST, which is ST 8. Very rapid gains for putting points into skill, and even some real benefit to the Dabbler perk, which allows raising your default level with a handful of skills. You could, of course, fiddle with this, and decide that DX or DX+1 was the assumed skill you need to get your full measure on the Damage Table.
In fact, in order to have the progression above play well with the ones assumed for Karate they have to be different. Karate gives you +1 per die to thrust damage at DX+1, and +2 per die to thrust at DX+2.
That is a cinematically awesome effective increase in ST. +1 per die is about +30%, while +2 per die is +60%. Wow. That’s a huge bonus for only DX+2. There’s not a great way to make this neat, so you’d wind up changing the progression a bit, probably making it more gentle, for Karate. Maybe you need to get to DX+4 or something, or instead of damage bonuses, you give ST bonuses, like Wrestling.
In any case, you can see why I just didn’t go there. It’s a rewrite, not an expansion. Still, that rewrite is kinda tempting . . .
This is my first video interview ever – not just for this blog. I will be attempting to add useful content to this post over time, including (eventually) a text transcript of the entire thing, since I find it entirely annoying when I have to play a video to get good content. So stay tuned.
Oh, and at the end, Sean throws down a bit of a challenge, which I will gleefully take up when I’m better at this: a panel discussion featuring more than one key player in the GURPS space. As was said about the Six Million Dollar Man, “we have the technology,” and there’s no reason such a good idea should go to waste.
I provided Sean a list of questions ahead of time, but other than a few moments where I forgot that the interview is not about what I have to say, I mostly let him talk. Here are some notable moments, messages, and themes:
- What is GURPS, in brief?
- Sean eats his own dogfood – Leveraging GURPS strengths into successful
- Secret to a long-running campaign (not GURPS specific)
- Sean offers his thoughts on GURPS’ weaknesses
- Generic systems can handle anything, right? (Hint: no.)
- Mechanical quirks with the system (3d6, Modifiers, system
comfort, point build)
- A few things with “no fair value” in GURPS or any point
- Doug tells a short story and forgets the interview isn’t
about him; Sean makes lemonade out of lemons
- Strengths and weaknesses of other game systems and where
GURPS does well and not-so-well (Doug mentions Pathfinder, GUMSHOE/Trail ofCthulhu, and FATE Core)
- FATE has more embedded complexity than some might think
- FATE is strong in the force (excels for dramatic play)
- Other game systems and drama/mechanics focus
- Doug pimps Impulse Buys and forgets he’s not being
interviewed again; Sean comments on GURPS ability to do dramatic play
- Sean talks about the importance of “realism” in today’s gaming industry and Doug butchers “plausible verisimilitude”
- What about that line in Basic about “the most realistic”game?“
- Sean talks about the rule of awesome and how this relates to
realism, good game design
- Why does Dungeon Fantasy, with soon-to-be 16 volumes, workso well? Rules, borders, and an end zone! (hat tip to Xander Harris, BtVS)
- Sean talks about the cleric of the god of love, and Doug’s
brain hurts as a result:
- Blending hack-and-slash with less combative types
- What other genres does Sean think will have the potential
for the same success as DF?
- What are the characteristics of future product lines that
might succeed given the “genre reduction” treatment?
- Sean talks about Space Opera
- Boiling it down: which genres work well, and which do not?
- Given the opening of the GURPS pipeline, what message does
Sean have for prospective creators and contributors?
- First-timers should follow the wish list:
- Read the style guide, and ensure you stick to it. Not fun,
but helps your product make a profit. Bad writing/english is easier to fix than
sloppy style! Style might even be more important than deadlines! (style guide links from wish list appended below)
- Write for your audience’s interests, not just for your own
- What kind of Zombie stories does Sean like? But what appears in GURPS Zombies?
- Why is this important for writing in a generic system,
especially in writing adventures? How can you make an adventure more generic?
Mirror of the Fire Demon is used as an example of a how-to.
- Parting shots?
- Sean closes with thanks, and throws down the gauntlet: a GURPS creator panel
I would be remiss if I didn’t thank Sean for giving me so much of his time to conduct this interview!
Again: in case you missed the embedded link, here’s a full-text transcript and an MP3 file of this same interview.
- Authors’ Guidelines: Editorial Style
- Writing for e23
- WYSIWYG Template for Microsoft Word (a Word template file)
- Formatting Guide: GURPS Fourth Edition (a Word document file)
- Steve Jackson Games Writers’ Guidelines: Libel and Obscenity
I never regret talking to +Peter V. Dell’Orto. Today were were chatting over Skype, and in a few short moments, a few things he said triggered a flow of ideas that will result in me revamping a long-pending Pyramid article. The article covers three topics. Well, maybe four. Has to do with weapons, using them and misusing them.
I’ve got the core of an idea, but the implementation required too many “well, this is necessary complexity. Trust me!” moments. Peter’s been on me for this for a bit now, and while the rules as written do work, something’s always nagging me that they could work better.
Now, I think, borrowing from a few other concepts already in the article, they will.
I’d say you can’t put a value on that, but you can: about $250. Maybe less once I strip out all of the truly unnecessary stuff out of the article. But in the end, it will provide a level of simplicity relative to what’s there now that will make the article much, much more likely to be actually used in play.
The moral of the story here is simple: Find a constructive critic who will help you pare your work down to bare, pure elements. Find a principle or three, and stick to them.
Three that I’ve learned from Peter?
The third one might be suspended in certain circumstances, such as when you can write a MapTools macro to take a few easy inputs and resolve many rolls automatically. But even so, the dice are there to facilitate the story and to keep things uncertain and risky. Stock option theory tells you that the value of a choice which is absolutely certain is zero. Same thing with dramatic storytelling, and why when (say) +George R R Martin kills off main characters in Book 1, it makes you sit up and take notice. All of a sudden your choices are far more important.
Anyway, I got a page of short notes and a real sense of how the new section is going to turn out. If nothing else, I have to wonder if I need to excise that new bit, plus one more rule, and just send it in. The other bits can wait.
Some of the greatest warriors of myth and legend were famed for their aptitude at grappling. Almost every historical culture had a patron god of wrestling (from Hermes to Hanuman) and accounts of heroes adept at the art (Herakles managed to strangle a dragon). Prior to the age of gunpowder, no professional soldier went into battle without some training in what to do when the hostilities moved to very close quarters indeed. Even today, policemen and soldiers learn to grapple, if only because that’s the most instinctive form of combat for human beings.
Despite all this, RPG protagonists tend to avoid holds, throws, and locks in favor of flashy strikes. In GURPS Martial Arts: Technical Grappling, Douglas Cole redresses this imbalance by expanding GURPS Martial Arts in ways that make grappling as exciting – and often as deadly – as gunslinging, swordplay, and fisticuffs. Inside you’ll find the new concept of Control Points (CP), which quantify your ability to twist and mangle your foe . . . and once you rack up enough CP, you can cut loose with all kinds of new combat options, perks, and techniques, whether your goal is to restrain your rival, incapacitate him, or brutally snap his neck.
This supplement contains all the rules and abilities you need to handle every kind of grappling, from ritualistic sumo to scrappy street fighting. It also covers the use of hardware, whether that means exploiting a police baton for extra oomph in an arm lock, entangling your opponent in a net or a kusari, or restraining a captive with rope or handcuffs. It offers optional “harsh realism” rules for everything from body weight to the effects of clothing and sweaty bodies on getting a firm grip. It even has something for fighters who aren’t ordinary humans, addressing Size Modifiers and superhuman abilities, and presenting grappling styles suited to bears, canines, constrictor snakes, and felines.
Why not grab a copy today?
Thus far, it would seem that at least 84 people have grabbed a copy. For that I am grateful!
I can’t think of a better GURPS Day present, of course.
I’ll be doing a lot of Technical Grappling related posts in the coming days, and I hope that you guys all enjoy the book.
So, now that I’ve regained my composure after some gratuitous fist-pumping and victory dancing, I am quite pleased to see that not only are we likely poised for a return to GURPS releases, but that my work was chosen/available to be that first release.
There are some interesting factoids and stories to tell about this manuscript, but I’ll not do that now. One thing I will say is that I’ve got roughly 5,000 words of designer’s notes ready to go, and they will appear in due course, either in some formal venue or on this blog. There will be some good stuff in there, including some content that was removed solely for wordcount reasons, not because they sucked. Well, there will be some of that too.
Master Grappling . . . or Face Defeat!
The canny warrior knows that grappling is fundamental to fighting. Any melee – from a brawl to a swordfight – could suddenly move into the clinch. Some fighters even specialize in such tactics!
This is a hard subject to get a hold on, however; volumes have been written about leverage alone. GURPS Martial Arts: Technical Grappling brings this depth toGURPS. Expansions to the GURPS Basic Set and GURPS Martial Arts rules include:
- Trained Strength. Discover how technical proficiency complements raw power.
- Control Points. Transform grappling from an all-or-nothing affair to a matter of degree.
- Position Revisited. Achieve leverage by jockeying for not only posture, but also facing and orientation.
- Armed Grappling. Control and entangle your foes with a surprising variety of melee weapons.
- Combat Options. Narrow your focus with the One Foe option, exploit Committed Attack to force a posture change, pass a limb to trap your opponent, and more.
- Techniques. More than 30 of them – some new, some modified. Use an Escaping Parry to break a clinch, or Change Position to establish a weight advantage.
- Fighting Styles. Learn Jacket Wrestling or Shuai Jiao – and distinguish between between bear and lion attacks – with six classic styles plus four specifically for animals.
Whether your campaign features athletes wrestling for prizes and honor, lawmen who must control and disarm suspects, or historical warriors trained to fight to the death, Martial Arts: Technical Grappling will add detail and realism to your battles.
This supplement requires GURPS Martial Arts for GURPS Fourth Edition.
We picked up where we left off in +Nathan Joy‘s game.
. . . Cadmus was praying, others were standing or hovering around, and a dragon that could move through ice like it was yogurt was, well, moving through the ice like yogurt.
It burst through right under Shiba ( +Mark Langsdorf ) and Thumvar ( +Theodore Briggs ), both of whom avoided the attack, Thumvar rolling a critical success. The dragon got to roll on the Unarmed Critical Miss table, and went sprawling. Staver shoots arrows at it, laced with alchemical fire. Thumvar does a double attack and totals 27 (2) cut. Shiba pounds it with another exploding arrow and does 9 imp and 10 bu.
Cadmus continues to pray to Pharasma that the dragon not be able to escape and burrow into the ice again. After a few seconds of this, a sense of peace descends on him. He also hears something rattle and hiss off in the direction to his left.
Thumvar nails him with two more blows, and Staver ( +Emily Smirle) hits with two more fire-arrows. Dragon drags himself off into the fog, and we lose track of him.
After a second or so, the dragon nails us all in a huge cone of solid cold. Cadmus is at the edge, and Dodge and Drops out of range. Thumvar gets out of the way, Shiba blocks the cone with his peshkali shield, and Staver eats 20 cold damage, which amulets and armor modify down so that he’s only at exactly 0 HP.
He doesn’t pass out. He does drink potions.
Thumvar nails the dragon one more time with a Feint and Attack with Shield and Sword, and nails the dragon on the skull for 14 (2) cut, and it falls limply to the ground.
Now, for the undead guy. Cadmus stalks forward . . . and the dracolich nails him with a a torrent of black ice. He gets hit for 17 burning damage, but his large-area DR (he learned from previous adventures) is DR 10 (DR 12 on head, neck, and torso; DR 9 on limbs) and he “only” takes 7 burning damage. He’s injured and frosty, but still fighting.
Cadmus recalls (after spending a destiny point to un-biff his roll) that these creatures can’t do their cone attack every second, but they can do it quite a bit. He then attacks the thing’s skull with his axe, but is parried. Meanwhile the dracolich attacks him with both claws and his teeth; cadmus does a riposting parry, a shield block, and a dodge to avoid all three attacks.
Staver tries to attack the skeletal dragon with fine meteoric arrows, but suspects that the impaling arrows won’t hurt his foe much. 8 (2) imp and 11 (2) imp to the vitals, such as they might be on a living dragon. It doesn’t bother to dodge, and doesn’t look like it’s hurt much.
Cadmus takes a turn as his compatriots gather to fight the dragon, and chops at its neck, hitting once for 10 (2) cut. It launches itself into the air, and moves FAST behind Cadmus. Thumvar flies past Cadmus’ field of view. We all overhear Thumvar muttering about how fast the creature is. Meanwhile we hear a loud crash and a sliding sound, as something seems to hit the ice and slide for a long way.
We then all hear a dull, echoing thud from somewhere up ahead, sounding even farther than the sound of the sliding.
Cadmus wonders if it slid into the crevasse like a big bony dummy. We find out that in fact, he body slammed the dead dragon into the crevasse, and either also went in himself, or is no longer anywhere to be found. Staver checks it out:
You look, and other than a carpet of coinage lining the dragon’s former nest, we see fresh blood indicating a large corpse was very recently dragged to the south of the crevasse where it vanishes under the side of the cave wall. Beyond that is a VERY tight fit you are a bit nervous about continuing down.
Strewn with bones, and the very bottom narrows into a wedge so you have to stop before you’re actually at the true bottom. You see a roughly two yard wide semicircular hole that you’re guessing a dragon could fit through if he squeezed. The edges are smeared with blood just beginning to turn tacky.
Cadmus kneels down and prays, long and fervently, to Pharasma to open the way for us. Widen the cave, block the exit, mark the path. Show us the way to this stinking undead for whom you have no tolerance, etc.
Cadmus’ prayer slowly draws to a close. There is a shivering CRACK that seems to come from everywhere at once. You all hear the squealing of ice moving over ice. Followed by a series of pops.From the cave mouth, and the tunnel, you hear another splintering crack, a deep silence for a few seconds, followed by a resounding boom of a large amount of ice hitting something very hard. Thumvar is slighly crouched in the tunnel mouth looking back at Shiba having a conversation with Cadmus, when there is a huge CRACK, and you see fracture lines race up the sides of the wall. You turn to look down the tunnel, and have a slight moment of vertigo as the tunnel seems to tilt slightly.Then the whole of the tunnel starting about a foot past your nose drops away, eerily silent, and in front of you is the main shaft of this chamber. You watch several hundred tons of ice pinwheel away below you to smash on the rocky crags hundreds of feet below. There’s a faint creaking, followed by several smaller pops coming from within the ice.Then silence.
- Cadmus stands up. He looks satisfied, awed, and determined. All at once.
- Shiba: “Ah? What is this?”
- Cadmus: “The Undead are accursed and must be destroyed. Pharasma paves the way for us to meet our destiny. Either that or we’ve just been sealed in the cave to die because I’ve asked too much too fast. You never know.”
- Shiba: “Oh. It is quite a marvellous miracle, then.” Pauses, works his jaw. “Would you be able to explain to this ignorant one what you have done?”
- Cadmus: “I have asked Pharasma to open the way for us. Widen the cave, block the exit, mark the path. Show us the way to this stinking undead for whom she has no tolerance
- Thumvar: “That’s not what I was expecting…”
- Cadmus: “Me neither. But then, anticipating Her Holiness is never wise. She delights in her games at times.”
We stare at the new geography, and wonder where our two dead dragons went. They could be anywhere in the complex, or buried hundreds (thousands?) of feet below in tons of ice.
We decide to break until next week to let the GM draw new maps!
Movement in GURPS combat is incredibly generous. Every turn, you may begin from a standing stop, travel in one second (or a part of it) up to your Move, which may be 4-7 yards, and wind up perfectly still and balanced, ready to either not move, continue your pace, turn, accelerate to attack speed, or whatever.
Is this realistic? Well, Usain Bolt in his first second of one of his world record sprints managed to cover about 40% of his assumed Move, which was calculated as his max velocity during that race divided by 1.2, to account for his sprint bonus. So even the best sprinter on the freakin’ planet should probably be limited to Move/2 for acceleration in realistic games.
Also, that kind of stop/start is tiring. You can easily exhaust yourself vibrating all over a sparring arena at the equivalent of a healthy jog (Move 4 is about 8mph, or an 7.5 minute mile; Move 6 is a 5 minute mile pace even without a sprint bonus!).
Anyway, so The Last Gasp has costs for movement that are, in a word, punishing. To do a run-around attack as described in the Basic Set can cost something like 8-9AP due to all of the movement and sharp turns, plus the attack itself.
So despite the emergent behavior that fights slow down a bit to allow people to recover their wind, the fact of the matter is there’s a huge disincentive for a character to stir from his starting spot at the beginning of combat.
There are two versions of the movement costs presented in the article, though the wording is (shame on me) not entirely clear. One version is that you pay for every step, at a cost of something like 1 yard for free, and 1 AP for each additional 20% of your Move. Or something like that. The other version is that you pay for acceleration, but further maintenance of that velocity is free. So you still can encounter the phenomenon of “activation energy,” where players won’t want to make the AP spend to get going.
So despite the Lulls and Flurries that are an observed emergent behavior of the Action Point rules, the battlefield might not be as mobile as you’d like.
Keep it Simple, Keep it Safe
So, what to do? Well, one suggestion on the forums was to make a “movement only” AP regeneration pool. That’s certainly one way to go, and probably adds the right level of points to the character sheet for those who have reduced movement costs. But if we try and keep it simple, I’d do something like this:
- Acceleration up to Move/2 is similar in concept to an Attack. It costs 1 AP. You still get your first step for free, and beyond that, any acceleration up to Move/2 costs that single point.
- Acceleration up to Move is like an All-Out Attack, and costs 2 AP. Again, you get the first step for free.
- Acceleration from full Move to Sprint speed costs 1 AP.
- Deceleration from movement other than a step costs 1 AP if you were moving up to your full Move, and 2 AP to stop dead from a sprint. That should probably involve a DX and/or HT roll to see if you can do this without injury. You may decelerate at up to 20% of your Move per second for free; sort of an anti-step.
- Facing changes can either be entirely free, or cost 1 AP for 2-3 facing changes in a move action, or 2 AP for 4+ changes within a move.
AP Maintenance Costs
Moving about is still tiring, but one way to deal with this is that at the beginning of each turn, if you’re moving more than one step at a time and wish to maintain that speed, make a HT roll. Succeed and the AP cost of your movement goes down by 1; succeed by 5+ and the AP cost of your movement goes down by 2. On a critical failure, you slow down by (say) 20% of your move, while on a critical success, you need not spend any AP to continue your speed next turn.
Another way to go, which is more in line with some of my original thoughts many moons ago, would be that you roll HT (or Running) every turn for sprinting, while at lower speeds, you roll every N turns (and I’d probably try and invoke the Speed/Range progression here somehow).
To create a mobile battlefield, there needs to be a lack of disincentives to move. If you can easily translate from place to place with limited AP spend, but actual fighting is AP intensive and creates incentives to pause, evaluate, and generally chill out, then you have created a situation where players and NPCs can come to each others aid, and repositioning doesn’t simply deliver an exhausted combatant to be ground to dust.
The current movement rules don’t help create that mobile battlefield, and may even be too restrictive even in a realistic mode. Flat-out lowering the AP costs for movement should go a long way to encourage people to fight for position as well as strength of arms.
The other thing that changing AP cost avoids that requiring something like AP Recovery advantage does not is that it can be dropped into existing games with existing characters. You don’t need some expensive (and some of the AP recovery rates are very expensive, on the order of a hundred points or more) advantage to be suddenly tacked on to your character. You just change the costs and go.
That being said, if one were looking for a switch, to allow differentiation between “can move about the battlefield like a ferret on crack” and “everyone else,” I’d probably tack on something equivalent in point cost to Trained by a Master. At 30 points, that’s like getting a 2/3 discount on recovering 5-10 AP per second for use only in movement. So if you’re looking for a design toggle:
New Advantage: Ferret on Crack
Will it work in play?
When +Hans-Christian Vortisch wrote Tactical Shooting, we came up with the Minute of Angle rule, which states that the maximum skill you can have with a firearm, including all modifiers except for range and size, can’t exceed 22 + 2*Acc. This was a calculation where I looked at the typical spread of a weapon in bench-rest mode, and converted it to a round target, usually at extreme range. As it turns out, if you know the spread of a weapon, you know it’s Acc, and there’s a very straightforward correlation between the two. Acc 5, for example, is about 1.5″ of shot spread at 100 yards.
And as a matter of fact, you can simply find the spread of a shot pattern at 100 yards by looking up -2*Acc on the Size table. Acc 4 firearm? Look up -8, and find that equivalent (in this case, 3.6″, or 0.1 yds) and that’s the circle that 90% of the shots will be in. Note that this means that the SM of that target is actually -10, but with +2 for being circular.
Showing the full work: 22+2*Acc = 22+2*4 = 30
At 100yds = -10 range penalty; Target Size penalty = X
90% chance to hit is 14 or less
So 30 – 10 + X = 14; X = -6
SM of -6 is a 3.6″ circle, because the SM of something 3.6″ in dimension is -8, +2 for being circular, thus -6. Therefore, the shot spread of an Acc 4 weapon is 3.6″ at 100 yds.
No problem. The spread can be found by taking -1* (10+2*Acc+Range Modifier) and looking that up on the Size table.
Acc 5 at 200 yards? (10+10-12 = 8*-1 = -8; SM -8 = ) 3.6″.
Acc 1 at 30 yards? 10.8″
Acc 2 at 25 yards (typical benchrest accuracy for a self-defense pistol of mediocre quality)?
It’ll produce a 5.4″ group (a little smaller, actually, but 25 yds rounds up to 30 yds on the Range table).
What does that have to do with anything?
Well, there’s a huge thread over in the SJG GURPS Forum about controlled bursts, shot spread, and all the usual stuff. As I ponder this, I think that the natural place to start is to figure out how disperse your bullets are, somehow compare that to the SM of your target, and roll to see if you hit.
Now, of course, combat isn’t about clamping a gun into a perfectly stiff and firm mount and pulling the trigger. Skill enters into it, and recoil, and motion, and . . .
But if we abstract all of that into a degradation of skill, perhaps what we wind up with, instead of using the Rcl mechanic, is an expression for the size of the burst due the inherent spread of the weapon, plus spread due to waving the thing around (control of recoil and steadiness, or purposeful lack of steadiness, of the mount), offset by a margin of error for misplacing the centerpoint of the target. Then you might compare that number to the SM of the target, which would give you a percentage of overlap between the shot pattern and your target. That should be a fairly straight-forward table lookup, perhaps. That would give you the percentage chance to hit with any one shot, and you could then find the chance to hit with many shots by rolling 3d6.
I actually did this in excel a while ago. So if, for example, you find that your pattern overlaps your target by 35%, and you fired three shots, you hit with one shot on a 12-, two shots on 8- and all three on a 5-.
The trick is to come up with the right way to get spread and displacement from the ideal aimpoint, and convert that to a hit chance. Then it’s just math.
Would you REALLY do this in play?
Not without a computer, no. But then, that’s getting more and more common, and all of this is just easy if what you’re entering into your tablet is a skill, a weapon (for Acc), a Range, and a number of shots for the attacker, and the SM of your target region for the defender.
Figuring out where specific shots hit would be a secondary complication, but that’s actually fairly doable. I’ve done something like it in the past, with an overlay that shows (with a d12 roll, sorry) where a shot might go depending on margin of success of a shot. That really only works for single shots, though.
Finding a mechanic that is both playable and realistic is tricky. What I might try and do is invoke agency, and players could perhaps take a penalty to skill to purposefully widen or narrow (!) their shot pattern (which might increase your odds of even being able to roll a hit, or compensate for a high-recoil/high-spread gun), and then the actual die roll is for how close the center of aim is to the target. You’d still wind up with, for rapid fire, multiple die rolls (bad), but I think you’d wind up with fewer edge cases. Open up on a SM+13 battleship, you’ll hit with every shot unless you completely biff the roll. You’ll even know how far from the ideal aimpoint you diverted, and how spread out your shots were. Assuming you care.
High skill individuals might purposefully take a penalty to spread shot around (saturation fire, hoping for suppression using the Fright Check rules from Tactical Shooting) or to control the shot spread, tightening the burst. Instead of Rcl being a MoS factor, it would be an increase in spread that occurs on multiple shots as a penalty to skill. You’d have to burn skill to compensate for it, which would impact your ability to keep your center of aim where you want.
Clearly this needs more fleshing out, probably tons of issues with it, etc. But it’s a potentially viable approach to the matter. I’ll have to see where this goes.
And just for fun, here’s the Acc to MoA table, which might be useful
With special guest star +Peter V. Dell’Orto
Amazing what you find on your computer. Your work computer no less. This file was dated from 2002.
I’m not sure the Quad ST idea will really have legs. Too mathematically intense, perhaps.
Quadratic Strength for GURPS
by Douglas Hampton Cole and Peter V. Dell'Orto