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Old 08-16-2010, 01:39 PM   #31
Langy
 
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Default Re: Engagement of Area Targets with Fully Automatic Fire

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Originally Posted by sir_pudding View Post
There is a reason why weapons like the M134 are used almost exclusively on aircraft. If the GURPS rules made them optimal for ground combat platforms that would then be unrealistic.
True enough, though I think that's probably more a case of overkill/too heavy for ground vehicles at the same penetrating power as an HMG rather than anything else.

Still, I used the example of a ground station in order to eliminate variance caused by the vehicle moving, which I figured you'd bring up again. A hovering helicopter might behave the same, though I'm not actually sure.

Quote:
"High" is a relative term here. MGs do have a high rate of fire compared to other ground combat direct fire weapons.
ROF 8 isn't 'high' even compared to other ground combat direct fire weapons. Assault rifles and SMGs typically have higher ROF than that.
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Old 08-16-2010, 01:42 PM   #32
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Default Re: Engagement of Area Targets with Fully Automatic Fire

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Originally Posted by sir_pudding View Post
There is a reason why weapons like the M134 are used almost exclusively on aircraft. If the GURPS rules made them optimal for ground combat platforms that would then be unrealistic.
I can think of a number of reasons. Enormous ammo-hunger giving them terrible staying power. You don't need RoF 66 for suppression! And the cannon-sized ones have lousy penetration for their size besides, which is usually the key feature wanted in a surface to surface gun that size (well, that or payload, and they're even worse there).

Whereas aircraft don't have staying power regardless, need to overcome lots of penalties to hit, and often won't even be able to Aim. So they need the RoF. Plus they get to top-attack armor, so they don't really need a 120mm gun for that.

But while it might not be a good idea, there's absolutely no reason you couldn't mount a rotary cannon on a fixed turret or vehicle mount and use it to engage ground targets. So why shouldn't GURPS give sane results if you do?
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Originally Posted by sir_pudding View Post
"High" is a relative term here. MGs do have a high rate of fire compared to other ground combat direct fire weapons. The sorts of weapons you are talking about are designed with a wide dispersion in order to allow a rapidly moving aircraft to effectively engage area targets (fireteams, squads, or platoons of dismounted infantry or combat vehicles).
High Tech doesn't much support that claim about rate of fire. The RoFs for most machineguns (except the powered multibarrel ones) are about the same as for assault rifles or SMGs.

They often get much greater sustained rates of fire due to their high ammo capacity, and are probably better for laying down heavy fire due to higher accuracy and often lower rcl...
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Originally Posted by safisher View Post
I think of those gun camera rolls from WWII, whether dogfight or ground attack, with bullets hissing from multiple MGs missing quite often. In single man vs. man context, its the three to seven feet pistol duels wherein no one gets hit.
I don't think anyone in this thread has proposed anything that conflicts with these events.
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Old 08-16-2010, 01:45 PM   #33
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Default Re: Engagement of Area Targets with Fully Automatic Fire

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Originally Posted by Langy View Post
ROF 8 isn't 'high' even compared to other ground combat direct fire weapons. Assault rifles and SMGs typically have higher ROF than that.
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Originally Posted by Ulzgoroth View Post
High Tech doesn't much support that claim about rate of fire. The RoFs for most machineguns (except the powered multibarrel ones) are about the same as for assault rifles or SMGs.

They often get much greater sustained rates of fire due to their high ammo capacity, and are probably better for laying down heavy fire due to higher accuracy and often lower rcl...
Rifles also have a high rate of fire, of course! MGs have a higher ROF than tank guns, rocket launchers, and missiles, i.e. specifically compared to other crew served support by fire weapons.
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Old 08-16-2010, 01:49 PM   #34
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Default Re: Engagement of Area Targets with Fully Automatic Fire

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Originally Posted by Ulzgoroth View Post
High Tech doesn't much support that claim about rate of fire. The RoFs for most machineguns (except the powered multibarrel ones) are about the same as for assault rifles or SMGs.
Don't forget that it's pretty common in fiction, either. Hell, they had a ground vehicle-mounted one in Myth-Busters, too, if I remember right.
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Old 08-16-2010, 05:20 PM   #35
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Default Re: Engagement of Area Targets with Fully Automatic Fire

One thing to consider here when looking at MoA type dispersions.

There are, basically, three regimes to consider for firing at a target. For the purposes of my discussion, I'm going to use a few terms, that might exist elsewhere, so please stick with my definitions:

1. Ideal Trajectory. This is the line that the "average" bullet with no dispersion in a perfectly still atmosphere at 75F blah blah blah will make. Basically, without accounting for any error. It, of course, connects from the barrel of the gun to EXACTLY where on the target you wish to hit. A bullet following the ideal trajectory CANNOT miss a stationary target. That's because it's IDEAL, with nothing getting in the way.

2. Average Actual Trajectory. This is the actual trajectory of the AVERAGE of all the shots fired

3. Cone of fire. The dispersion of shots around the Actual Trajectory, caused basically by the combination of errors for shooter movement, target movement, improper alignment of the gun, natural dispersion of the weapon (bench-rest MoA). The MoA (or mils) inherent to the weapon/ammo combination can often (and IS often) determined and quoted empirically, for example, 22MoA for the M134.



OK...so, how does one "hit" or "miss" in GURPS?

0. We presume there is, in fact, an Ideal Trajectory that exists.

1. The Average Actual Trajectory is perfectly aligned with the Ideal Trajectory, and (a)the target is either larger than the Cone of Fire (100% chance of hitting) or (b) the target is smaller than the cone of fire at that range, but the bullet happens to hit anyway (less than 100% chance, dictated basically by the percentage of the target that lies inside the circle)

2. The Average Actual Trajectory is imperfectly aligned with the Ideal Trajectory (the actual line of fire deviated from point of aim) but (a) the target is STILL way bigger than the Cone of Fire, even imperfectly centered (100% hit), (b) the dispersion of that particular shot within the Cone of Fire falls on the target anyway (less than 100% chance, with probability still figured as below).

3. The AAT is imperfectly aligned with the Ideal Trajectory AND the Cone of Fire does not ever intersect the target. Total whiff. Impossible for any bullet to strike home.

If you more or less know the range and the Average Actual Trajectory (previous fire, rangefinding devices and computerized targeting), you'll know that when you hit "Fire," the bullets will strike home.

If you don't know the Avg Actual Trajectory, because (say), your fighter is threading its way through AAA while trying to lay down 20mm SAPHE rounds on a target that is also maneuvering, then most of the "misses" are because of misalignment between the Average Actual Trajectory and the Ideal Trajectory. You might get a lucky hit, but by and large your gun is simply pointed the wrong way.

The case above is THE DEFAULT for combat. They're moving, you're moving (or could), and you're not assumed to have perfect knowledge of the dispersion and fall of shot. In this case, which is in fact MOST OF THE TIME, the GURPS bog-standard rules are fine. You don't CARE whether the miss came from pointing the gun in the wrong direction, or dispersion of shot...you just know that they missed, and the rest of the bullets are subject to the 'hitting the wrong target' rule.

What we're talking about is an edge case, where we are assuming that the target is so large that misalignment between the Average and Ideal trajectories, as well as Cone of Fire, will all fall within the target.

Tactical Shooting will have a rule (but I'm not tellin' what it is) that addresses what happens when you push the MoA part of the weapon, but you may be skilled enough that the Average Actual Trajectory and the Ideal Trajectory are exactly right (so case 1b above).

What would be useful, then, it seems, is some way of knowing the effective Size Modifier of the ATTACK itself; if the SM of the Actual Cone of Fire is less than the SM of the target, 100% of the hits strike the target somewhere. If it's equal or larger, you're probably rolling under standard GURPS rules.

This would be fairly easy if GURPS didn't lump all forms of inaccuracy together, which it does for game play sanity reasons. Good game play sanity reasons. But, what you need to do is figure out how far off the point of aim is from Ideal, apply Cone of Fire to that, and see if you're still within the SM of the target.

If so, you still hit with ALL the bullets. If not, roll on the table the usual way and take your lumps.
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Old 08-16-2010, 05:40 PM   #36
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Default Re: Engagement of Area Targets with Fully Automatic Fire

Wow, it seems like between Low-Tech and Tactical Shooting there won't be any questions about GURPS left for us to address on the forum.
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Old 08-16-2010, 05:43 PM   #37
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Default Re: Engagement of Area Targets with Fully Automatic Fire

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Wow, it seems like between Low-Tech and Tactical Shooting there won't be any questions about GURPS left for us to address on the forum.
That thur w'd be un' o' them gud problems, sonny.
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Old 08-16-2010, 06:11 PM   #38
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Default Re: Engagement of Area Targets with Fully Automatic Fire

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Originally Posted by DouglasCole View Post
Tactical Shooting will have a rule (but I'm not tellin' what it is) that addresses what happens when you push the MoA part of the weapon, but you may be skilled enough that the Average Actual Trajectory and the Ideal Trajectory are exactly right (so case 1b above).
This is excellent news! Does it handle things like firing a minigun into a person's eye at 600 yards (where a really skilled shooter might hit with 10+ bullets, all in the eye, rather than some of those bullets hitting the head/chest/missing completely due to dispersion)? In other words, will you be able to say 'these bullets hit the eye, these hit the face, these hit the torso, the rest miss' or something like that?

Quote:
If you don't know the Avg Actual Trajectory, because (say), your fighter is threading its way through AAA while trying to lay down 20mm SAPHE rounds on a target that is also maneuvering, then most of the "misses" are because of misalignment between the Average Actual Trajectory and the Ideal Trajectory. You might get a lucky hit, but by and large your gun is simply pointed the wrong way.

The case above is THE DEFAULT for combat. They're moving, you're moving (or could), and you're not assumed to have perfect knowledge of the dispersion and fall of shot. In this case, which is in fact MOST OF THE TIME, the GURPS bog-standard rules are fine. You don't CARE whether the miss came from pointing the gun in the wrong direction, or dispersion of shot...you just know that they missed, and the rest of the bullets are subject to the 'hitting the wrong target' rule.
I figured this was the case, but the problem I have is GURPS seems to assume you can only keep the weapon centered on-target for a very small portion of a turn when dealing with high ROF weapons, but you can keep it centered on-target for the full second for lower-ROF weapons. Either that, or you're able to get the target centered at the perfect time for when the weapon cycles every single time, while whenever the weapon isn't physically firing the weapon is off-target, which sounds a bit silly.
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Old 08-16-2010, 06:38 PM   #39
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Default Re: Engagement of Area Targets with Fully Automatic Fire

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What would be useful, then, it seems, is some way of knowing the effective Size Modifier of the ATTACK itself; if the SM of the Actual Cone of Fire is less than the SM of the target, 100% of the hits strike the target somewhere. If it's equal or larger, you're probably rolling under standard GURPS rules.

This would be fairly easy if GURPS didn't lump all forms of inaccuracy together, which it does for game play sanity reasons. Good game play sanity reasons. But, what you need to do is figure out how far off the point of aim is from Ideal, apply Cone of Fire to that, and see if you're still within the SM of the target.

If so, you still hit with ALL the bullets. If not, roll on the table the usual way and take your lumps.
Now is the rule for "Actual Cone of Fire" something you guys also already did for Tactical Shooting?, or is this something which you're still thinking on?

This sounds like a whole new stat which we'd have to add for certain types of weapons, though I'm sure the gunbunnies would be happy to have a reason to modify choke on their shotguns...

ACoF - Actual Cone of Fire
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Old 08-16-2010, 09:43 PM   #40
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Default Re: Engagement of Area Targets with Fully Automatic Fire

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Now is the rule for "Actual Cone of Fire" something you guys also already did for Tactical Shooting?, or is this something which you're still thinking on?

This sounds like a whole new stat which we'd have to add for certain types of weapons, though I'm sure the gunbunnies would be happy to have a reason to modify choke on their shotguns...

ACoF - Actual Cone of Fire
I have postulated, and GURPS supports, a direct conversion of Acc to MoA. Technically, as with the, I think, spaghetti sauce, "it's in there."

Acc 2 or 3 works for pistols, Acc 4 for SMGs and Carbines, Acc 5 for rifles, and acc 6-8 for precision weapons of ever more ridiculous lack of dispersion.

If you actually look up (or use a proxy for) the actual MoA of weapons, and look at the Acc values given them? While the relationship might be complicated (power law, log function, whatever), it's there and it works.
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