RogerBW's Blog

Call of Cthulhu has a spotty history with automatic fire; it's one of the few rules that changed quite a lot between editions before the complete rewrite that was 7th. I don't think 7th has improved matters.

Now I'm not afraid of a bit of complexity if it's explained well. Sometimes it isn't; automatic fire in GURPS 4th edition confused a lot of people, and an explanation of it was one of the first things I wrote for the blog. So let's break this down. If you want to follow along, I'm using the Core Rulebook (Revised), pp. 114-116. (If you know the GURPS rules these will look remarkably familiar in places, and then suddenly very different.)

So the first thing you need to do is choose whether you're using "full auto", "burst fire" or "semi-auto". The last of these doesn't use this procedure; it just has the standard effect of firing multiple shots with a handgun, which adds a single penalty die to each shot after the first. "Burst fire" is a short, controlled burst, while full auto is continuous fire, and the weapon stat will tell you what the weapon can do.

OK, so you're doing actual automatic fire. Pick your targets, all of whom need to be in about a 60° cone. Traversing from one target to another will waste one bullet per metre, so you need to take that into account in the number of bullets you're firing in the calculations below.

Full-automatic: choose how many bullets you're firing, up to the number remaining in the weapon. Divide these into "volleys" of at least 3 bullets, the size being at most the tens digit of your relevant skill (SMG/MG). Fewer bigger volleys are more likely to hit and do more damage. Allocate each volley to a target.

Burst fire: as above but the volley size is a fixed number determined by the weapon, typically two or three.

[ So let's say you're firing a MAC-11 ("1(3) or full auto") with 32 rounds in the magazine, and you have SMG skill 50. You have a line of cultists, each a metre from the next. You can choose volleys of 3, 4 or 5. You choose 4. You can allocate a volley of 4 at the first cultist, lose 1 bullet for the traverse, a volley of 4 into the second, 1 for the traverse, and so on, until you run out of targets or rounds in the magazine. ]

You have now assigned a bunch of volleys each to its target, and you roll to hit for each of them separately. The first roll is a standard attack; second has one penalty die; third has two penalty dice; fourth has two penalty dice and +1 difficulty level (e.g. if you needed a Normal success to hit you now need a Hard success). Fifth has two penalty dice and +2 difficulty levels, and so on.

For each of these attacks, a plain success means that half the shots in the volley hit (rounded down, minimum one); roll damage for each of them. An Extreme success (if you didn't already need an Extreme to hit in the first place) means that half (rounded down, minimum one) will hit and impale, and the rest will just hit normally.

This has inspired me to construct a test for rules: what aspect of gaming does the rule serve?

• Is it gamist? Yeah, a bit, but it doesn't give you interesting choices to make. You should always fire the largest even-number-sized volleys you can, and as few separate volleys as you can get away with.

• Is it narrativist? No, because the output you want in story terms takes the form "one or two of them fall down" or "none of them falls down", and this is a highly involved way of getting there.

• Is it simulationist? No, because volleys don't represent anything you'd do in the real world. This is just about OK for handheld automatic weapons but really has nothing to say about bracing, bipods/tripods, suppressive fire, different levels of recoil for different sorts of weapons…

I think that this rule falls between too many stools and ends up satisfying nobody.