Action Report: Suppression Fire in GURPS
Last night in the Ceteri game, my character had the opportunity to unload an RoF 15 weapon in a narrow cone with something like five or six targets in it. It was a good chance to use the rules for suppression fire, which basically give you a 6+RoF bonus chance to hit there.
We use some generally agreed-upon rules – a combination of “this is the way we think the rules are actually meant to be applied,” common sense, and a slight tweak on the RoF bonus table.
The RoF Tweak
It’s not much. Look up the number of bullets fired on the Size and Speed/Range table, and read out the size modifier. Divide it by two, but round UP. Yes, up. That’s not the usual, but it works.
That produces a chart like this:
| Shots | RoF Bonus | Max Rounds/Min |
| 1-2 | 0 | 120 |
| 3-6 | 1 | 360 |
| 7-14 | 2 | 840 |
| 15-29 | 3 | 1740 |
| 30-69 | 4 | 4140 |
It’s got a lot in common with the normal rules. Past a certain point, you need to double the shots fired to get the extra +1. One or two shots gets nothing, but the “three-round burst” actually gets a bonus, which is nice.\
If you want to bother with it, if you fire a cone, simply take the total bullets fired, divide by the width of the cone at the point where your target is, and your RoF bonus is based on that. So if I’m unloading 15 bullets into a cone three hexes wide where I’m shooting, it’s 5 per hex, ergo only +1 RoF bonus there, or “Roll 7 or less to hit.”
In the Zone
The basic application here is that if the target is in the cone when it’s laid down, it gets attacked. If it’s a multi-hex creature, it gets attacked for each hex in the zone. That’s not news.
The way we apply the rule – how Christopher, I, and Merlin all have come to both interpret the actual rule and the sense of it – is that that cone is persistent. A target that is not in the cone when it’s initially laid down will be attacked for every hex that moves into a hex in the suppressed zone.
The zone is two yards wide? If you didn’t start in the zone and you cross it, you’ll be attacked twice. You started in the zone (and therefore were attacked when it was laid down), move into the left side of the zone, then out? You get attacked once for the move into the left zone, but not for moving out of it (ergo that stepping dodge, dodge and drop, take cover, etc).
If you move up the zone, advancing on the firing person, for five yards? You will be attacked five more times.
Fear the Bullets
Quite simply, if you are within the zone or a yard of it, and you are capable of feeling fear, you will have to make a fright check. Fail and you must leave the zone by the most direct path, take cover, or be stunned. This simulates the panic under fire that can happen. I’d probably leave the “freeze as bullets rain down” for failures by 5+, but basically, that zip-zip-crack of the bullets whizzing by is great incentive to get the hell out of there.
One of the forumites and a fairly frequent interlocutor and former infantryman notes that some definitions of “suppression” are basically “0-9% casualties.” That is, you’re really not hitting on better than a 6 or less anyway. So the fright check is important for creating the necessary behavior on the part of not-superhumans exposed to gunfire.
Parting Shot
The tactic was effective last night. I laid down a corridor through a cone of bad guys that killed or injured two and made three or four more at least rethink their life choices. I don’t recall having to do it twice, but if I had, I’d have run out of bullets the second time (30-round magazine).
It had precisely the desired effect – at least one disrupted (basically right next to me) and the rest either hit or ducking. The presence of the persistent cone of fire, drawn on the VTT screen, was a visible reminder of area denial . . . and yet one of our allies crossed it to get to his son, with no harm done. Lucky, but he made it.
It’s a quick application and interpretation of the existing rules, but it just feels right in play, and since the emergent behavior is all one could ask for, we use it.
I like it. It’s more or less how we have played it when it has come up.
There was a forum thread on the topic, and mostly Kromm noted that the way described is at least a valid interpretation of what goes on. The RoF chart is, I think, just better, in terms of scaling with GURPS rules and gives the +1 for the 3-rnd burst. The fright check thing is just stolen from Tactical Shooting. Works well enough.
Something that had been bugging me for a long time is that there’s no benefit for a “double-tap”—I’ve been wanting to see any instance of >1 round get a minimum of +1, but I haven’t really delved into the unintended consequences on that yet.
With pistols in GURPS, two shots gives you considerably more confidence that the target will stop being a problem.
Which is the point of failure drills in real life too.
First, just wanted to say that what you’ve described is pretty much exactly how I’ve been gaming suppression fire in my games. The one exception is that I only did one attack to someone who entered the cone of fire, and not once per hex. I’ll be implementing that immediately.
One thing I’ve wondered about, but never worried too much because it’s never really come up in my game, is what happens when the RoF divided by width gives an effective RoF that’s less than 1. It’s unlikely to occur when the target zone is centered on opponents at range. But, in a hypothetical situation, what if he made his cone 3 hexes wide 1 hex away (really desperate against that horde of zombies that just closed into melee range)? He’s basically covering a 180-degree cone, and the bullets that don’t hit would likely keep travelling quite a bit further away. So at 10 hexes away in this situation, the RoF is effectively a small fraction. Do we apply penalties to the effective skill of 6 (at which point, may as well declare an automatic miss). But what about the fright checks? I’ve now suppressed a 180-degree angle. Should there be a bonus based on the fraction (RoF of 1/2 = +2, RoF of 1/5 = +5?).
Additionally, I’ve been starting to question why suppression fire is treated differently than any normal gunshots.
If I pick a single target and fire at his hex with Suppression Fire, I attack him with a maximum effective skill of (6 + 3 =) 9, even if my skill, say, 25. Even if I miss, he needs to make a Fright Check roll to not take cover. Finally, if any bullets miss, then I get to roll to hit anyone else who enters into the line of fire until my next turn.
On the other hand, if I pick that same target and fire 15 rounds directly at him then I get to attack with my skill of 25 + 3 = 28 (minus range penalty, etc.), which means a better chance to hit. But if I miss, he doesn’t have to make any Fright Check or bother to take cover. And if any bullets miss, I don’t get to attack anyone else who crosses the line of fire before my next turn.
These are basically almost two identical scenarios with widely different game effects. I’ve therefore been contemplating – but haven’t yet implement – a rule where anyone in the line of fire of any gun shot (or laser beams, or lightning bolt spells, etc.) has to make a fright roll to not take cover, and that, if a bullet hasn’t hit a specified target, than there’s a “live fire” line of attack that anyone who crosses becomes a potential target. To me, All-Out Attack (Suppression Fire) just allows you to divide your shots over a wider area, reducing your chances of hitting in exchange for possibly affecting more people with fright checks.
My one hesitation is that it would possibly slow combat down in order to track all the lines/arcs of fire. But since I use MapTools for my combat, I don’t think it would be that complicated.
This needs its own post to respond properly!