In his Melee Academy post for July, +Peter V. Dell’Orto touches on enfilade fire, that is, shooting through a whole bunch of targets. GURPS can get a little wonky (or a lot wonky) when you apply rules that are pretty much built around point fire from one single source (usually a PC with a gun) against another point target (the designated NPC victim, most often).
He comments that it would be an interesting post to look at how GURPS does this in various ways, and see about what the best one would be for each. This is going to assume at least two shots, but may be many shots, since some high tech weapons can have RoF in the range of 60-100, that is, 3,600 to 6,000 bullets per minute. Even your bog-standard assault rifle types can have RoF 10-13, and rapid-cycling automatics firing pistol cartridges (like the MAC-11) can hit RoF 20.
Current Rules Options: Point Targets
GURPS has a couple ways of dealing with point targets – three that I can think of offhand. Let’s see what they are – or seem to be (more on that later).
The simplest and best covered, and easiest to rationalize. Roll your skill, adjusted for many, many things (range, rate of fire, target location, aiming bonuses, target size, movement penalties, etc). If you succeed by 0, you hit once. For every margin of success equal to the gun’s Rcl, you hit with one more shot. Most non-sci-fi weapons have at least Rcl 2, so to hit with many bullets, you need to have a very high skill.
This reasonably accurately represents that most times, firing lots and lots of bullets at a target is not really done to hit lots and lots of times, but rather to increase the chances of hitting a few times.
For most situations, the point fire rules work just fine. Any bullets that miss are supposed to default to the Hitting the Wrong Target rules on pp. B389-390.
What happens when you miss?
Well, actually, that’s a darn good question. The rules for Hitting the Wrong Target and Overshooting and Stray Shots (p. B390) really seem to be tailored very much to arrows and such. One shot at a time. The Wrong Target rules make it very much seem like “which unlucky soul between you and your target got hit,” but since certainly you could miss high, the line of fire likely extends past him as well (how far?). The Overshooting rule refers to the projectile pretty consistently, and neither are really written with a mind to the assumption that in all likelihood, more shots miss than hit even on a successful attack.
So perhaps neither of these is really a great idea for guns and rapid fire. In fact, right now, I’m leaning towards “these don’t apply.”
OK, so I attack his hex! HA!
It’s sometimes funny how this blog works (or doesn’t. Your call.), since I’d never really stared at that rule before. Of course you can attack the hex someone’s in at +4, right?
Well, I don’t think so. Not for many weapons – only those that can engage in plunging fire, or as the Box on p. 414 makes clear, you “lobbed it in a high arc.” I’m not convinced that the +4 is due to the size of the hex, either. I think it’s the fact that it ain’t moving. That rule also says that attacking an area is for area-effect and explosive attacks – and area effect seems to have a pretty precise definition, and ‘firing lots of bullets at lots of hexes’ doesn’t really seem to apply.
So what about attacking a hex? It’s the very definition of a one-yard target, with the +2 bonus for blob, box, or sphere. So a hex is, well, SM+0 and attacked at neither a penalty or a bonus for size. Again, pretty sure that +4 is for immobility, not dimension.
Thing is, if you miss the hex, you’re supposed to use the scatter rules. Scatter for a hail of bullets? Actually, that’s not a bad concept in general. Let’s hold on to that for later.
How does any of this apply to Peter’s original question about what rules to use when attacking lots of guys in an area? Well, it doesn’t.
Current Rules Options: Dispersed or Area Targets
OK, so if the previous discussion hit shooting that guy over there, what about shooting at that whole bunch of guys with the torches, pitchforks, and thermal detonators?
Looks like you sort of have two options.
Spraying Fire (p. B409)
Within a 30-degree arc, you may choose to spread fire among as many targets as you like. Thing is, you waste a bunch of shots going from target to target, which is fine. However, you get to choose how many bullets of those not wasted you can sling at each one. Yow. That’s cool under fire, all right. You make a separate attack roll against each target at the effective RoF you dedicated. You can only do this if you have RoF 5 or higher.
Suppression Fire (p. B409)
The other way provided to attack an area is to mark out a two-yard-wide area, and shoot at it. You can fire up to your weapon’s full RoF, and you can attack basically a two-yard-wide swath from you to your target with a fairly low hit rate: 6 + the RoF bonus of your weapon. For every extra RoF 5, you may add another two-yard zone as long as you fire at least 5 bullets into each zone.
The point target rules work quite well, but a lot of the other stuff (even for point targets) squeak around the edges a bit. I think the existing concepts can be combined and recombined usefully here.
Missing and Point Fire
The Stray Shots and Wrong Target rules should probably be rationalized a bit. Maybe if you miss against a point target, you roll the same 1d6 for Scatter. 1 means you missed high (over the target); 4 means you missed low (short), 3/5 mean you were short and right/left, while 2/6 are long and right/left.
I’ll leave how much the attack missed by for another time. That can get ugly if done wrong.
Still, that would allow a GM to adjudicate where the line of fire went.
These are actually some of my favorite rules, and I think that they should be used more broadly. Any time you fire at a target, bullets that don’t hit your intended target create a cone of fire/suppressed zone that is hazardous to cross. If you enter that zone before the shooter’s next turn, you take suppression fire.
Yucky yucky. Too much fine control over bullets. To pull that off, use Ranged Rapid Strike, not the rules here. Then it makes more sense to choose between targets and allocate bullets. What I would do instead is something like picking a line of hexes N hexes wide, dividing the bullets evenly between them, and looking up the RoF bonus per equivalent hex. Look up the length of the line on the Size and Speed/Range Table and roll against 8 + the Range penalty + RoF bonuses (so a line 10 yards wide will roll vs a 4 + RoF bonus).
If you miss, and there are targets behind the ones you’re shooting at, extend the cone of fire, and re-calculate at the new range, and roll again.
Example: You are spraying fire into a cone which is five yards wide at your target location with a gun with an impressive RoF 60. That’s 12 shots for a +2 RoF bonus in each hex, against a base roll of 6. So for each target in this zone, you’re rolling vs. an 8-. If there is another target at twice the distance you’re shooting at, the width of the line doubles, and you now roll against a base of 4, but you’re now only putting 6 bullets into each hex, so your RoF bonus drops as well, and at this range, the spray fire bonus is only +1, so now you’re at 5-. Too much farther and you’re just missing or crit fishing.
You might be able to apply this to a mass of people as well. Figure out the width you’re dividing your fire, and if that width changes much going to the back of your formation. Figure out the general odds of each rank, roll appropriately. Work your way backwards. Either that, or just divide the total bullets by the total number of targets, and most likely you don’t get any RoF bonuses. Just roll based on line width for each target. +Sean Punch notes that the targets are actively moving around within their hex to a resolution or mesh size of more or less +/-1 hex at all times, so if in the die rolling that follows, you find that the guy in the back got plugged but the guys up front didn’t, well, them’s the breaks.
GURPS is a game, not a ballistics simulation (my best efforts to the contrary notwithstanding!) and so there will likely be nothing short of such a simulation that will give plausible results for launching a hail of bullets downrange more or less skillfully. Not within the time constraints imposed by your friends revolting and beating you about the head with the hardcover GURPS rules while pelting you with d4s.
So the best you can hope for is something that gets you in the ballpark. My own preference would be to try and find a ruleset where you effectively either do point fire, even for suppession, or spray fire, with the attendant drops in per-target hit chance. The Wrong Target/Stray Shots rules can be directed either using a scatter mechanic (shooting low/left means that you can’t overshoot past the target, overshooting might mean that the first threatened zone is hundreds of yards away, etc.) or as they are now, but utilizing the suppression rules to pick your shots.
I don’t want to have “I want to use the Wrong Target rules, instead of suppression” be a viable choice.
So, did I answer Peter’s question? I fear not, but it was fun to noodle on this GURPS-Day!