The Hit Location rules allow for shot placement based on the attacker's margin of success. In GURPS, margin of success is used to determin how many shots hit when firing more than one round per action. This will lead to an odd correlation between the two in the game. To correct for this, you can use the following ...
When firing more than one shot per turn, at least one shot hits if your hit roll succeeds. The chance on 1d6 that other shots fired will hit is the margin of success. Subtract 1 from this chance-in-6 to hit if the weapon is rcl 2, subtract 2 if the weapon is rcl 3. If the chance-in-6 is 6 or more, all shots hit. If it is 0, there is a 1 in 6 chance for every two additional shots that one of those two shots hits. For every additional -1, double the number of shots needed for a 1 in 6 chance that one shot hits to a maximum of -4. You need the full number of shots to have a chance to hit - if you shoot seven rounds but have a 1-in-6 chance to hit for every eight shots, you have no chance of getting extra hits. Exception: If you only fire one additional shot, there is a 1 in 12 chance that the one extra shot hits (roll a 1 on a 1d6, then roll a 3 or less to confirm this hit).
When firing 4 or more shots, you do not get a bonus to hit. Instead, you pump enough lead toward your target that even on a margin of success of -1 or less you have a chance for additional shots to hit. This is summed up in the table below:
Recoil Modified Margin of Success | Chance-in-6 | |
6+ | Automatic | |
5 | 1-5 on 1d6 | |
4 | 1-4 on 1d6 | |
3 | 1-3 on 1d6 | |
2 | 1-2 on 1d6 | |
1 | 1 on 1d6 | |
0 | 1d6 for every 2 shots | |
-1 | 1d6 for every 4 shots | |
-2 | 1d6 for every 8 shots | |
-3 | 1d6 for every 16 shots | |
-4 | 1d6 for every 32 shots |
If you targeted a particular hit location and achieved sufficient margin of success to hit it straight out, count the margin of success beyond what you needed to hit the target location, modified for recoil, as the chance on 1d6 for subsequent shots to strike that hit location. If this results in only one of a number of shots having a chance to hit, use the die roll for the first shot in the group.
Example: If you shoot three shots at the center torso with a rcl 3 firearm and get a margin of success of 7, your first shot hits the vitals. Your recoil modified margin of success is 7-2=5, so your second and third shots have a 5 in 6 chance of also hitting your target. You need a margin of success of 2 to strike the torso, so these shots have a 5-2=3 in 6 chance of striking the torso outright. You need a margin of success of 5 to hit the vitals, 5-5=0, so you have a 1 in 6 chance of one of the two shots also striking the vitals. Roll the die for the first bullet. On a 1, it hits the vitals. On a 2 or 3, it hits the torso with the usual random chance to strike the vitals. On a 4 or 5, it hits a random hit location. On a 6, it misses. The second shot hits the torso on a 1, 2, or 3, a random hit location on a 4 or 5, and misses on a 6. |
Example: If you shoot three shots at the center torso with a rcl 3 firearm and get a margin of success of 3, your first shot hits the torso. Your recoil modified margin of success is 3-2=1, so your second and third shots have a 1 in 6 chance of hitting. With a necessary margin of success of 2 to hit the torso, these additional shots do not get to hit the torso outright. They will only strike the torso if random shot placement puts them there. |
Shotguns and other multiple projectile weapons use a variation on this rule. If you barely hit with a shotgun at close range, the shot pattern is still so tight that all pellets will impact the target, and probably all in the same hit location. Contrarywise, even with a perfect shot at long range, the shot will have spread enough that you have no guarentee of actually hitting. To reflect this, shotguns have a spread statistic, which indicates how fast the projectiles spread out. The spread gives the range modifier at which the projectiles have expanded far enough from each other to fill a 3 meter circle. A typical shotgun has a spread of 11. With a partial choke, the spread becomes 12, with a full choke, the spread is 13.
The spread plus the range and size modifiers give the chance on 1d6 that each projectile hits. As with rapid fire, if this number is 0, you have a 1 in 6 chance that one of every two projectiles hits, with the number of projectiles doubling for each additional -1 to get a 1 in 6 chance of one hit. You do not automatically hit with one pellet even if you succeed in your attack roll. However, if firing very large numbers of pellets you can still get a chance to hit even if the spread plus the range and size modifier is less than -4.
Example: If you fire a shotgun with spread 11 at a coyote (size modifier -1) standing 50 meters away (range modifier -8), each pellet has a 11-8-1=2 in 6 chance of hitting. |
Find where the shot cone for each shot is centered normally, using the normal hit location rules. Modify the chance-in-6 to hit as follows:
Example: You fire two shots of 9 pellets each from your spread 11 shotgun at a biker thug bearing down on you at 15 meters range (range modifier -5). Both shots hit, one striking the face and the other the torso.
The torso has no hit penalty, so each pellet has a 11-5=6 in 6 chance of striking the biker somewhere. The margin of success to hit the torso is 2, so each pellet has a 6-2=4 in 6 chance of hitting the torso. When you roll the 1d6 to determine if each pellet hits, a 1 means you hit the torso but not the vitals, a 2, 3, or 4 means you hit the torso and have a 1 in 6 chance of hitting the vitals, a 5 or 6 means you hit a random hit location. The face has a hit penalty of -2, so each pellet has a 11-5-2=4 in 6 chance of striking the biker somewhere. It takes a margin of success of 3 to hit the head, so each pellet has a 4-3=1 in 6 chance of striking a random hit location on the head. It takes a RMOS of 5 to hit the face, 4-5 is less than 0, so no roll on the 1d6 directly indicates a face hit, although the face can be hit randomly due to the head hits. When you roll the 1d6 for each pellet to hit, a 1 indicates a head hit with the usual chance to strike the skull, face, or neck, a 2, 3, or 4 is a random hit somewhere on the body, and a 5 or 6 is a miss. |
Special: for very distant or very small targets
When the magnitude of the combined size and range penalty is equal to or larger than the spread, you only need to roll to hit as if the SM of the target was spread - range penalty. If the target is not moving, this is the same as if your combined penalty for size and range were equal to the spread of your gun. This does not modify the chance in 6 for each projectile to hit, but the shot cone is so large at that point that the small size of the target makes it irrelevant to targeting. In this case, every pellet that hits strikes a random hit location.
Example: You fire a shot from your spread 11 shotgun at a grouse (size modifier -5) perched 50 meters away (range modifier -8). The combined range and size penalty is -13, but you only have to roll to hit with a penalty of -11 to skill for range and size. If you succeed, the spread plus the range and size modifier is 11-8-5=-2, for a 1 in 6 chance to hit for every full 8 pellets fired. If firing 9 bucksot pellets, you would have a 1 in 6 chance of scoring a hit. This is why hunters use birdshot on birds! |
Example: You fire a shot from your spread 11 shotgun at a hornet (size modifier -12) zooming past you at 5 m/s when it is 3 m away (normally range modifier -1, increased to -3 because of speed). You can treat the hornet as if it were SM 11 (for spread) - 1 (for range) = 10. Your total hit penalty is -10 (for modified SM) - 3 (for combined speed/range) = -13. |
Fragmentation from an explosion, and any other blast of projectiles that are shot out randomly in all directions, use the multiple projectile rules with a spread of zero. Assume there are 10 fragments per die of explosive damage.
Note that this is an overestimate of the chance to hit, but an underestimate of the number of fragments, the two assumptions cancel out. Realistically, the spread should be -3 and the number of fragments increased, but this is harder to remember.
When spraying fire or using suppressive fire, choose an area into which you are directing your fire. Determine the size modifier of this area. Make an attack roll against the area, not targets in it. If you hit the area, everything in the cone from your weapon to the area and beyond has a chance to be hit as if you were firing a multiple projectile attack with a spread equal to zero minus the size modifier of the area minus the range modifier to the area.