RogerBW's Blog

GURPS 4th edition introduced a completely new mechanism for the resolution of attacks with rapid-firing and automatic weapons, and uses the same one for shotgun pellet hits (which are after all a similar sort of multi-projectile attack). Here's how it works.

You have numbers for rate of fire (RoF) and Recoil (Rcl). RoF is how fast the weapon fires: it determines how many bullets (or shotgun pellets, laser bolts, or whatever -- I'll just say "shots" from now on) can be fired as part of a single attack. Normally you can freely choose any number from 1 to the RoF (in case you want to conserve ammunition, for example). The more shots you fire, the better your chances of getting a hit at all: that's the rapid fire bonus, seen in the table on p. B373.

Rcl determines how hard the weapon is to control: the higher the number, the more it tends to drift off-target when firing fast.

You make a single attack roll just as you normally would. Add the rapid fire bonus, if any. If you miss, you've missed with all your shots. If you hit, you've hit with at least one shot; work out the margin of success. Each full multiple of Rcl that you succeed by gives you an extra hit. (And that's why laser weapons don't have "Rcl 0" even though they may have zero actual recoil: that value would just mean that you automatically hit with all shots, which would be meaningless.)

So for example you have skill 14, and you're firing a generic TL9 auto pistol (RoF 3, Rcl 2) at a target ten yards away (-4). RoF 3 isn't enough to give you a rate of fire bonus, so you have effective skill 10. If you roll 10 or 9, you've hit with one bullet; 8 or 7, hit with two; 6 or less, hit with 3.

Now the target gets to defend, as usual. He only makes a single defence against the whole attack. Making the defence roll exactly lets him evade just one shot; each +1 on his margin of success lets him evade one more. (Note that it's much easier to evade multiple hits than to achieve them in the first place.)

Let's say you hit with three bullets. Your target has a Dodge of 9. If he rolls 10+, he's hit by all three. On a 9, he's hit by two; an 8, by one; a 7 or below, by none.

Any remaining hits progress individually to armour, damage, and so on.

That's the basics. As you can see, you have one more decision to make compared with a normal gun attack: How many shots do I fire? Quite often, the answer is "a three-round burst"; with typical realistic skill levels, you're unlikely to hit with more than three shots anyway. Super-skilled and super-accurate characters can get away with longer bursts. Five and nine shots are worth using, since they're the first breakpoints for getting a bonus to hit.

There are some special cases. Some weapons can only fire in full automatic mode (such as the TL6 9mm SMG on p. B278); they have a ! after their RoF stat. You can still fire less than the full RoF by just briefly stroking the trigger, but the minimum number of shots in an attack is 1/4 of RoF (rounded up). (Obviously you can't fire more shots than are left in the magazine.)

If your target is totally immobile (inanimate, restrained, or unconscious), and your range penalty is fully counteracted by the target's size modifier (for example, a normal human is within two yards), then a successful attack roll means that half the shots fired hit; if you succeed by Rcl or more, all the shots hit.

Weapons firing multiple-projectile (pellet) rounds have a RoF with a multiplier, for example 3×9. The first number is the number of units of ammunition (e.g. shotgun shells) fired (and as usual you can choose a number from 1 to that value); the second number is the number of projectiles per shell. Multiply the two together to get the effective RoF of the attack, which will generally give a rapid-fire bonus to hit even if you only fire one cartridge. After that, just resolve as above.

A multiple-projectile round that's fired at a very close target won't have time for the projectiles to separate; they strike like a large but inefficient single projectile. If your target is at less than 10% of the 1/2D range, instead of increasing RoF as above, use half the multiple-projectile value as a multiplier to damage and to the target's DR.

If you have a weapon with RoF 5+, you can spray multiple targets with a single burst. They must all be within a 30° angle, and you have to engage them in order. Determine the RoF you're using, and split it as you like between your targets; but if they're more than a yard apart, you must allocate one wasted shot for each empty yard you traverse, two wasted shots if you're firing with RoF 16+.

Once you've done that, make a separate attack roll for each target: your RoF for each one is the number of shots you allocated to the attack. There's no penalty to hit, but Rcl goes up by one for each target after the first: so your Rcl 2 weapon is effectively Rcl 3 for the second target, Rcl 4 for the third, and so on.

Also if your weapon has RoF 5+, you can perform Suppression Fire. Select a target zone two yards across. (If your weapon has RoF 10+, you can attack multiple adjacent zones; each one must get at least five shots.) Then take the All-Out Attack (Suppression Fire) manoeuvre, which takes a whole second; you can't do anything else, including defending yourself, until your next turn.

If anyone enters any of the zones, or the space between you and the zones, between this moment and the beginning of your next turn, they automatically get attacked. Ignore modifiers for target visibility, but everything else applies, including any aiming you did before you fired and any bonus for RoF (just the RoF going into that specific zone, but that'll still be at least +1). However, your final skill can't exceed 6 + rapid fire bonus for hand-held weapons, 8 + rapid fire bonus for tripod- or vehicle-mounted weapons.

If you hit, you must roll random hit locations, as it's not possible to choose where (or even whom) you hit -- and some of your shots may strike cover as a result. If all your shots somehow hit something (either the target or the cover they're hiding behind), you can't hit anyone else with the rest of that suppression fire action.