Over on the SJG forums, there’s an interesting (if long) debate over the observation that all things being equal, it’s always better to fire lots of bullets at a target than just one, or even a short burst.
For example, let’s take a 500-yard shot, made by someone with Guns(Rifle)-13. That might seem a low score, but it’s probably not.
500 yards is a -14 range penalty, so you will need to rack up some serious bonuses even to have a chance of hitting.
So we’ll give our shooter a decent rifle – say the Barrett REC-7, from Tactical Shooting, and we’ll slap a 10x scope on it. That’s a 6.8x43mm SPC cartridge, Acc 4, +3 for a scope, 780-yd 1/2D range. It’s also got RoF 12, which at full tilt will be good for a +2 bonus.
So, no matter, what, we’ll have our shooter Aim for three seconds (+4 for basic Acc, +2 for extra time, and another +3 for the scope), as well as Brace (+1) with All-Out Attack (Determined) for another +1. Total bonuses are +11, which brings the odds of hitting, neglecting Rapid Fire, to a net penalty of -3 including range and accuracy, for a final hit chance of 50%.
Lean on the trigger, though, and you collect the +2, which boosts the hit roll to 12-, which is a 75% chance of hitting at least once. The Rcl of the rifle is 2, so you actually have a 50% chance of hitting twice, 25% chance of three hits, 10% (ish) of four.
Note that in terms of efficiency, single shots will hit a net of 50% per bullet. For autofire, if you do a weighted average (for this given example) of number of hits, it works out to about 1.6 hits per attack, that is, if you roll a 12 or 11, you hit once, 10 or 9, twice, etc. If you take the probability of any one roll times the number of hits for that roll, then add ’em up, you get about 1.6 hits. So autofire on a per attack basis is more than three times more effective on a per-attack basis.
The cost of that, of course, is that you spend 9-12x more ammo to get there. So our single-shot weapon will be using 2 shots per hit. Our autofire weapon is using 5.5-7.5 shots per hit. That is, by the way, at about 18 rounds per pound of this ammo. So 1/3-lb of ammo per hit.
OK, so there’s a trade-off, and a tangible one, assuming you care about running out of ammunition. In my own games, that has not once been an issue. +Peter V. Dell’Orto, whose character sported a TL8-9 version of the REC7 used in the example, solved this problem with a ST 17 (or so) character using 100-round drums of ammo – you’ve got about sixteen dead guys (or at least hit guys, at 6d per hit) per reload. For a rifle with a 25-round magazine, you’ve got 12 dead guys (or at least hit guys) per reload. Not really rate limiting. In +Mark Langsdorf‘s Mecha Against the Giants campaign, he had to take fairly drastic steps to force ammunition supply to be an issue. All you have to do is build your guy assuming magazines weigh 6-lbs each instead of about a pound.
So What’s the Problem?
No, the real issue is that the autofire bonus is not offset by any sort of “my weapon is jumping around like a ferret on crack” effect, and the trade off in ammunition expenditure doesn’t hold in check behavior not seen in the real world. (But see below for more on this.)
What would this look like? More importantly, how can we smoothly transition from “short, controlled bursts actually do work well” to “you’re shooting mostly at the sky” without tedious and math-intensive crank-turning?
Break Up the Rolls
Well, for one, the first shot or burst of shots – probably up to the four shots you get with Rapid Fire that don’t give a bonus – shouldn’t be any different than direct fire at a point target. After that, you could either apply scaled penalties, or more likely treat all remaining shots using the Suppressive Fire rules, or alternate rules.
So for any given attack, you’d make one roll for the first number of shots up to 4 (the point after which bonuses kick in), and then treat shot 5 and onward using the suppressive fire rules.
The advantage here is that firing short, controlled bursts or autofire has roughly the same chance of hitting for that first few shots, but after that you’re really in suppression mode, and odds are your hit chances go down rapidly. In our example above, the first four shots are treated as Guns-10, while after that, the remaining 8 shots (RoF bonus of +1 using RAW) are treated as a Suppression Fire attack with a net roll of 7 – 6 + the RoF bonus.
Basically the feel here is “fire the first four shots as you like; after that, you’re just hoping to get lucky.”
Is that perfect? Nope. High rate of fire bursts with stabilized weapons – or even radar-steered weapons – should probably have a much higher cap, even beyond the +2 bonus you get for a mount. Things that let you do “eyes-open” correction, probably including a Reflex sight, should probably raise the skill cap. It might be interesting to use, instead of a flat 6, something like the weapon’s base Acc-1 – taking into account that a lot of vehicle-mounted weapons will be fired as All-Out Attack (Determined), plus Braced.
So a mounted M2HB would fire at 6+RoF bonuses, while a Maxim Mk1 would fire at 5+Bonuses, and if you mounted up a low-accuracy SMG or high-accuracy pistol with Acc 3, you’d be shooting at 4+RoF bonuses.
The bit in Ultra-Tech about active targeting adding Acc? That’ll work too, and add ALL of Acc, including Aim/Scope bonuses. So your computer guided M2HB is 11+RoF bonus. But since the first four shots are fired using point-target methods, that’s really a 11 cap if you’re filling the sky with ..50BMG under radar guidance, mechanical control, etc.
Still, most normal humans won’t have to worry about that.
Other Gun Control
There’s also an alternate rule in Pyramid #3/65: Alternate GURPS III assigning a -2 penalty to autofire (making it a Technique), which would fix this case, and all guns with cyclic, or full-auto, rate of less than 950 rounds per minute (RoF 15), which is where the +2 cutoff sits. That’s probably good for most guns, except for high-cyclic weapons such as the MAC-11 or Glock 18 (both with RoF 20). Of course, neither is famous for controllability in full-auto fire.
Thing is, though – there’s zero disincentive to mash the triggers on these weapons. RoF 20 gives you a whopping +4 bonus on a Rcl 2 weapon. That is, on the average, you’ll hit three times instead of one, all other things being equal.
This doesn’t really help with “more bullets are better” as the general rule, it just moves the scale down.
The other possibility would be to do something with Rcl. For example, Rcl is the listed value on any given table plus (say) half the RoF bonus you get for Rapid Fire (round UP). So a Rcl 3 weapon fired with an RoF bonus of 1 or 2 would turn into Rcl 4.
For our example, firing at RoF 5-12 (+1 or +2 bonus) would push our REC7’s Rcl to 3 instead of 2. That wouldn’t change the +2 bonus you get for rapid fire, but it would mean you only get 1.2 hits per RoF 9-12 burst instead of 1.6. Adding RoF bonus to Rcl directly will drop that to one hit per burst. That’s still twice as effective per attack, but it’s five times less efficient in terms of ammo expenditure.
That might work OK, as a quick and dirty.
I think several people have proposed this, but having the Rapid Fire bonus scale with half the Size and Speed Range Table bonus for the number of bullets fired is probably a better progression than the one on p. B373, based on how GURPS works.
The other thing to consider is that lots of unskilled folks really do just hose down the area with a wild spray of bullets. They don’t hit much either – at least not intentionally. Again, that’s why I favor the suppression fire rules.
In fact, that might be a nice consideration. Unless you do an All-Out Attack (using the rules that sighted shooting must be All-Out, from Tactical Shooting), or an optional allowance of a Ranged Committed Attack, you must use suppression fire if firing at RoF 4 or higher.If you use sighted shooting or aim, you get that first four rounds as direct fire on a point target.
I don’t think I solved the problem here. But I definitely agree that it causes some unusual behavior. Trained troops are taught to fire short, controlled bursts, even with tripod or other mounted weapons, if I’m not mistaken. GURPS rules tend to push you to full-auto whenever you can pull it off, which leads to the interesting observation that given a Vickers Mk I.303 machinegun (Acc 6 – but go ahead and mount a scope on it) and an AI AW (Acc 6, +3 for a scope), your better bet for ‘sniping’ is the machinegun, because the AI only has RoF 1, while the Vickers is 10, for a bonus and likely an extra hit, or at least hitting more often.
Fixing Rcl doesn’t offset the bonus RoF gives you. Treating the first few shots as aimed fire (and no RoF bonus for it) and everything else as “hoping to get lucky” is probably the most satisfying, but it does require an extra roll.