[Tactical Shooting/Pretensions of Realism!] Suppressive Fire

[Eukie]

In that elusive realm known as "real life", nearly all fire with firearms at someone will suppress them in some way. Being fired at is scary, even when the bullets don't hit. People are largely unwilling to expose themselves when bullets are flying. Despite suppressive fire and the suppressive effects of shooting being integral parts of modern warfare, few games address the intimidating effects of firearms, being more concerned with the immediately deadliness, or at best, allowing characters to make special intimidating Suppressive Fire attacks.

GURPS is among the former, although Tactical Shooting suggests using Fright Checks when targeted by Suppression Fire or shots which narrowly miss (p. TS34, "Cool Under Fire"). One of the problems with accurately modeling the suppressive effects of firearms is that there is little to no literature on the subject. Certainly, that the effect exists is well-established, but its details and its magnitude are largely undocumented. After all, it's very hard to measure empirically the various factors that contribute to a soldier's reaction to being fired on.

That's not to say that nobody has tried though, and after several hours of very boring searches, I found a scientific article on the subject; The Identification of Objective Relationships Between Small Arms Fire Characteristics And Effectiveness Of Suppressive Fire, an ARPA report from 1972 (declassified 1984, approved for public release 2003). It deals extensively with how green and veteran soldiers (both Army and Marines) responded to and perceived the dangerous/suppressive effects of various kinds of enemy fire - as part of their research, the authors even surveyed ARVN soldiers and NVA POW's about how they reacted to various kinds of suppressive fire.

This report let me construct a rough measurement of the suppressive effects of any given firearms attack on a normal human target. The measure of suppression is:

[dmg of gun]/10-[greater of target's Will and Will-based Soldier skill]/3-[margin of failure on Guns/Gunner roll to hit the target]+[ROF hit bonus (p. B373)]+2

Where dmg treats each 1d as 3.5. Round all fractions up. The margin of failure of a shot that actually hits the target is 0. I'd also suggest applying various standard Fright Check modifiers as suggested by Tactical Shooting. Then, roll and add 3d6 and consult the following table:

<2     No effect
2-3    On your turn, you must move to any cover within reach, or Dodge and Drop (B377). On your turn, you cannot move.
4-6    On your turn, you must move to any cover within reach, or Dodge and Drop. On your turn, you cannot move or make any attacks except Pop-Up Attacks (B390)
7-9    As above. In addition, you can only make glances to gain Situational Awareness. (TS11)
10     On your turn, you must move to any cover within reach, or Dodge and Drop. On your turn, you cannot move or make any attacks.
11     On your turn, you must move to any cover within reach, or Dodge and Drop. On your turn, you cannot move or make any attacks. In addition, you can only make glances to gain Situational Awareness.
12+    On your turn, you must move to any cover within reach, or Dodge and Drop. On your turn, you cannot move or make any attacks. You cannot even glance to look at the enemy.

As an exception to the above restrictions on cover, if you are completely behind cover, you can move freely as long as you remain in cover.

As long as you are being fired upon, you must keep rolling, applying the most recent effect to limit your actions. If you are fired upon by multiple attackers in a single turn, use the highest roll to determine how suppressed you are. The effects of being suppressed last a single turn. After that turn, if no new attacks are made against you (or such attacks are made, but have no suppressive effect), you're no longer suppressed and can move and attack freely.

These rules were cobbled together somewhat hastily, so I appologise if things are not entirely clear. If there are any questions, I will try to communicate my intent as clearly as possible. I fear I'm not as well-versed in GURPS as I should be, so there might have been some rules that have eluded me so far.

Currently, in terms of realism, the main constraint is that this system does not realistically model for how long suppression lasts, or how officers can rally soldiers.

Rationales/Notes:

Perhaps most interesting for game purposes are the experiments where live ammunition (!) was fired at volunteers (!!) to determine their reactions based on type of ammunition, rate of fire, and miss distance. The results are treated empirically with statistical measurements, which means they are ideal for use in a role-playing game like GURPS, where things are usually resolved with numbers and rolling dice.

I originally developed this system for use with Phoenix Command, but out of curiosity I decided to see how easy it would be to convert it to GURPS; the answer was "very", so here goes:

The ARPA report divided the effects of suppression into 7 distinct categories:

• "Take cover as best I could, but wouldn't be able to observe or fire on the enemy at all. "
• "Take cover as best I could and would be aole to observe
  the enemy occasionaly, but wouldn't be able to fire
  at the enemy at all."
• "Take cover as best I could and would be able to observe
  the enemy continuously but wouldn't-be able to fire at
  the enemy at all."
• "Take cover as best I could, and would be able to observe
  the enemy occasionally and fire at the enemy occasionally."
• "Take cover as best I could, and would be able to observe
  the enemy continually and fire at the enemy occasionally."
• "Take cover as best I could, but would be able to observe I
  the enemy continually and place continuous fire on the
  enemy."
• "Would continue doing what I had been doing before the incoming fire and wouldn't worry about getting better cover."

These were then assigned numerical values from 0 to 100 to reflect their actual severity; 100, 90, 80, 59, 34, 17, and 0. Then the results of firing bullets at soldiers were statistically fitted with several parameters to produce equations representing the effects. The most important factors were:

• The soldier's GT score (a measure of their mathematical aptitude, their verbal knowledge, and their reading comprehension)
• The number of months of combat experience they had
• The distance at which the bullets missed
• The number of bullets fired
• The type of weapon used (five were tested; the XM19, the M16, the AK47, the M60, and the M2)

The soldier's GT score corresponds well to their IQ, and the number of bullets fired is of course just the RoF. The distance at which bullets miss very closely corresponds to the margin of failure on the Guns/Gunner roll, due to statistical peculiarities I won't get into here.

Although not in the ARPA report itself, it was easy to fit the kinetic energy of the bullets to the measured "scariness" of the bullets in the test. It (although one should be careful about drawing conclusions just from 5 data points...) is a very close logarithmic fit. Sadly, GURPS weapons do not have logarithmic measurements of the kinetic energy of every single firearm ever published (Phoenix Command conveniently does...). The dmg of a GURPS firearm is fairly well known to be proportional to the square root of the kinetic energy... but for low values, the square root approximates the logarithmic function! Taking the dmg values from High Tech (which has stats for all the weapons used in the test!) can be used to find a fairly accurate linear fit.

In addition to this, since the experiment included a large test group (over 1400 soldiers), they could calculate things like standard deviation of responses to being fired at - the standard deviation is roughly 25 on the 0-100 scale. GURPS 3d6 have a standard deviation of about 3, so that gives us a conversion factor between GURPS values and the 0-100 scale.

Since GURPS distinguishes between intelligence and resolve, we want to use Will instead of IQ to account for the soldier's intelligence. There's no real measure of combat experience in GURPS, so let's simply use Will-based Soldier to represent training and experience with being fired upon. The ARPA report treats the volume of fire as a strictly linear scale, but primarily concerns itself with small values. It is "common sense" that nobody are going to be particularly more scared by 101 bullets than 100 (and the brain works logarithmically), so we can use the logarithmic ROF hit bonus table from Campaigns to account for the number of bullets fired. Conveniently, it doesn't need a conversion factor.

[sir_pudding]

Originally Posted by Eukie

GURPS is among the former, although Tactical Shooting suggests using Fright Checks when targeted by Suppression Fire or shots which narrowly miss (p. TS34, "Cool Under Fire").

There's also the rules on p. 21 under Fire and Maneuver which can impose a Will-2 roll to expose yourself to fire at all, and can also result in falling down and losing several turns getting back into position to bound again.

Also it's important to note that once a shooter is Stunned due to a failed Fright Check or Surprise or whatever they no longer get the Heat of Battle Fright Check bonus (see Threat Recognition p. 33-34) which can trigger a very realistic (and deadly) panic spiral. I highly recommend combining some of the options in Not Just Stunned on GURPS Horror p. 141 with the rules in GURPS Tactical Shooting.

[Captain Joy]

Originally Posted by Eukie

The ARPA report divided the effects of suppression into 7 distinct categories:

Your last two bullet points are identical, by the way.

Your post was amazing; worthy of a pyramid article after incorporating some of the advice I'm sure this thread will generate.

[Eukie]

Originally Posted by sir_pudding

There's also the rules on p. 21 under Fire and Maneuver which can impose a Will-2 roll to expose yourself to fire at all, and can also result in falling down and losing several turns getting back into position to bound again.

Also it's important to note that once a shooter is Stunned due to a failed Fright Check or Surprise or whatever they no longer get the Heat of Battle Fright Check bonus (see Threat Recognition p. 33-34) which can trigger a very realistic (and deadly) panic spiral. I highly recommend combining some of the options in Not Just Stunned on GURPS Horror p. 141 with the rules in GURPS Tactical Shooting.

I'll have to take a look at them then!

Originally Posted by Captain Joy

Your last two bullet points are identical, by the way.

Your post was amazing; worthy of a pyramid article after incorporating some of the advice I'm sure this thread will generate.

I've fixed the bullet points; they should now read correctly. As for a Pyramid article... I have never written such a thing, it doesn't seem to fit anything on the wishlist, and I am somewhat intimidated by the submission guidelines. They are long and there's a giant eye in a pyramid staring at me! :P

[The_Ryujin]

Originally Posted by Eukie

As for a Pyramid article... I have never written such a thing, it doesn't seem to fit anything on the wishlist

You might want to take a look at the thread I started over on the Pyramid board, I'm trying to fix that little fact :D

and I am somewhat intimidated by the submission guidelines. They are long and there's a giant eye in a pyramid staring at me! :P

Well... There are those who can help you with that. Take a look into the Pyramid mentoring group, I plan on trying it out once I have proper net again.

[DouglasCole]

Quick thing I noted:

[dmg of gun]/10-[greater of target's Will and Will-based Soldier skill]/3

That's the first part of your roll to suppress, and you treat Damage as dice x 3.5

Dice x 3.5 / 10 is basically dice/2.85, which is close enough to Dice/3 that you might consider

[Dice of Damage - Will or Will-based soldier]/3

[gilbertocarlos]

I don't know where you took the data of a few stats, but I can see a few simplifications to the formula.

First, why the +2? couldn't you remove it and also give -2 on all stat from the table?

Second, instead of dmg/10 or dice/3, why not use 1 for sidearms, 2 for rifles, 3 for heavy rifles and 4 for HMGs? It's easier to consult than calculate, and it's the correct result 90%+ of the time.
Pistols goes from 6(.32) to 15(.50AE) All of with is rounded to 1
Rifles go from 15(M1 carbine) to 25(Garand), rounded to 2
heavy rifles are around 31(.338), rounded to 3
HMG are around 42(.50), rounded to 4

Or, better yet, reduce one from all above and also from the table, and instead having 0 for sidearms, 1 for rifles, 2 for heavy rifles and 3 for HMG, meaning that on a sidearm firefight you can ignore this stat.

Third, RoF seems to be double dipping, remember, RoF already gives a bonus on the to hit roll, and the to hit roll is already calculated, why give the bonus again.
Take a effective skill of 12 that rolled 15, it would be a -3 by the failure margin, but if he used automatic firing for +2 RoF, he would have changed this -3 to -1, should the bonus be greater?

Fourth, why allow a base will roll? shouldn't a civilian have a really hard time to shoot back? I think a will-based soldier roll should always be the case.

Fifth, shouldn't he be able to roll will instead of being forced by his stat?

Taking point 1 to 4, we can have a simplified and more easily applied formula:

[gun modifier]-[Will-based Soldier skill]/3-[margin of failure on the roll to hit]=Rating on the table below.

-2 or less No effect
-1 or 0 Must move to any cover in reach or Dodge and Drop (B377). Otherwise, can't move.
1-3 Must move to any cover in reach or Dodge and Drop. Can only make Pop-Up attacks
4-6 Above. In addition, can only make glances to gain Situational Awareness. (TS11)
7 Must move to any cover in reach, or Dodge and Drop. Cannot move or attack.
8 Must move to any cover in reach, or Dodge and Drop. Cannot move or attack. In addition, you can only make glances to gain Situational Awareness.
9+ On your turn, you must move to any cover within reach, or Dodge and Drop. Otherwise, you cannot do anything.



Now that I ended the post, something strange hit me, most of the time there would be no effect, let's take a 9mm missing Joe average by 1.
Using the standard formula it would be -1, no effect.
Using my modified formula, it would be 0-1-1= -2, still, no effect, but almost.
So, it seems that either Joe average can almost be hit and still act normally, or the formula is wrong. I bet all my chips on option 2.
Also, it's impossible to roll the highest rolls on it, let's take a coward(Will 6) being shot by .50BMG at 100 bullets per second and being almost hit(failure by 1), clearly, one of the worst cases, and the result would be 10 in the standard formula, still it's not the worst effect.

[sir_pudding]

GURPS tries to avoid rules that say "Your character does this exact thing" in favor of rules that say "You have a penalty to do anything except this exact thing".

I'm also wondering if this is really needed with the the existing rules for Fire and Manuever and Cool Under Fire, especially if used with Not Just Stunned and Stress and Derangment from Horror. Also the Last Gasp rules seem good here too. With this stuff, I'm wondering if GURPS doesn't already produce realistic results. In my experience it produces very real feeling results, anyway.

[Eukie]

Originally Posted by gilbertocarlos

Second, instead of dmg/10 or dice/3, why not use 1 for sidearms, 2 for rifles, 3 for heavy rifles and 4 for HMGs? It's easier to consult than calculate, and it's the correct result 90%+ of the time.
Pistols goes from 6(.32) to 15(.50AE) All of with is rounded to 1
Rifles go from 15(M1 carbine) to 25(Garand), rounded to 2
heavy rifles are around 31(.338), rounded to 3
HMG are around 42(.50), rounded to 4

I wanted the system to be fairly universal and accurate. For example, if you have an extremely powerful Ultra Tech weapon that's also a pistol, and a shoddy High Tech HMG, this system was designed such that the UT super-pistol would be more suppressive than the HMG. As is, you could even use this for suppressive fire with bows or super-power energy blasts.

Even when just used with normal, modern firearms, it makes some weapons within the same class have differences. For example, the M2 Browning from High Tech has suppression of 5, not 4, and the .50 AE, despite being a pistol round, suppresses like a rifle, since 1.5 rounds to 2.

Originally Posted by gilbertocarlos

Third, RoF seems to be double dipping, remember, RoF already gives a bonus on the to hit roll, and the to hit roll is already calculated, why give the bonus again.
Take a effective skill of 12 that rolled 15, it would be a -3 by the failure margin, but if he used automatic firing for +2 RoF, he would have changed this -3 to -1, should the bonus be greater?

Hmm. That's a bit of an interesting question. The way I intended it was that first the ROF increases the chance that a bullet passes close by the target. Then, independently of this, the ROF makes the attack scarier.

However, I expect that in the experiment, the burst spread at the target was kept low enough that it was not possible to discern between whether it was the closest bullet that mattered, or whether it was the general location of the burst that mattered. The former would justify adding ROF, the latter would imply it shouldn't.

Originally Posted by gilbertocarlos

Fifth, shouldn't he be able to roll will instead of being forced by his stat?

<snip>

Now that I ended the post, something strange hit me, most of the time there would be no effect, let's take a 9mm missing Joe average by 1.

You roll and add 3d6 before looking up in the table. I apologise if that was not clear.

Originally Posted by sir_pudding

GURPS tries to avoid rules that say "Your character does this exact thing" in favor of rules that say "You have a penalty to do anything except this exact thing".

Hmm, this is true. I am not sure how to account for this. One option I've considered is having suppression always cause the Stun effect but give the option to also either flee (towards cover) or drop the ground - similar to the Horror rules like you suggested. I'm not sure whether that would be too restrictive though.

On a similar note, how about disallowing actions? For example, if I want to say that while suppressed, you can't make All-Out Attacks, would that be against the GURPS orthodoxy? How about requiring dice rolls, like "You have to succeed on a Will-based Soldier roll to take a Step out from cover. If you fail, you have to do something else that turn."?

Originally Posted by sir_pudding

I'm also wondering if this is really needed with the the existing rules for Fire and Manuever and Cool Under Fire, especially if used with Not Just Stunned and Stress and Derangment from Horror. Also the Last Gasp rules seem good here too. With this stuff, I'm wondering if GURPS doesn't already produce realistic results. In my experience it produces very real feeling results, anyway.

I was not concerned as much with "real feeling" results as results that I could have confidence actually reflected reality to within what I considered acceptable bounds - in this case, that meant rolling 3d6 on a linear table with a fairly simple set of modifiers based on the factors considered significant in the paper I read. The most pressing example of where these rules significantly differ from Tactical Shooting is that TS makes all weapons equally suppressive, from a .22 pistol to a 20mm autocannon. These rules attempt to account for that.

[Varyon]

Originally Posted by Eukie

Hmm. That's a bit of an interesting question. The way I intended it was that first the ROF increases the chance that a bullet passes close by the target. Then, independently of this, the ROF makes the attack scarier.

However, I expect that in the experiment, the burst spread at the target was kept low enough that it was not possible to discern between whether it was the closest bullet that mattered, or whether it was the general location of the burst that mattered. The former would justify adding ROF, the latter would imply it shouldn't.

I think the "double dipping" makes a good deal of sense, honestly. Fully automatic fire is scary. You hear a rifle going off constantly, hear bullets slamming into your meager cover, and hear near-misses whizzing past your ear. Sounds to me like it should be far more suppressive than a rifle going off every second and hitting as close as the closest bullets from the automatic.


As to your original system, the only change that jumps out at me is handling being suppressed by multiple targets. That's a lot of rolls, and I feel penalizes the target too much. I'd say keep the first roll, and later attacks will modify this - if they miss by more, no effect, if they miss by less, a bonus. Simply add their RoF to the original RoF to determine the bonus from that.

For example, let's say our intrepid hero with Will-based Soldier-18 is under fire by 5 insurgents. They're armed with AK-47's going at full RoF (10). The first insurgent misses by 3, the second by 5, the third by 2, the fourth by 1, and the last hits with a single bullet, but fortunately our hero's trauma plate stops that hit cold. Upon the first hit, he'll be at (5.3-18)/3-3+2+2, or -3. He rolls 3d and gets an 8, so he's at 5. The next guy missed by more, so no change there, but he boosted RoF from 10 (+2) to 20 (+4), so now our hero is at 7. Dude #3 missed by only 2, so that's a +1, and boosted RoF to 30 (+5), so now our hero is at 9. Dude #4 missed by only 1, for another +1, but boosting RoF to 40 (+5) has no effect, so we're at 10. Finally, the last guy hit, so MoF 0, and boosted RoF to 50 (+6), for a grand total of 12. For simplicity, we could have simply used the full RoF of all insurgents (50) and the MoF of the best shot (0) for our roll from the beginning and got the same result.

While working that example, I had a question - what about when a foe "hits" but you successfully Dodge? What is his MoF there? I'm thinking we should go with 1, regardless of how well the character Dodged.