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Old 01-19-2017, 01:20 PM   #1
Onkl
 
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Default Rate of Fire with selective fire weapons

Hi guys

I am currently trying to understand Tactical Shooting, having played a few testrounds with friends, a question about Rate of Fire and full automatic mode came up.

Let's take the MP5A5 as an example.

It has RoF 9/13 (HT123), meaning that it has a selector which enables the operator to select single shot fire (RoF 3 without the Fast-Firing technique), burst mode (RoF 9, firing 3 bursts in short succession), and full automatic (RoF 13).

Since the full automatic mode does not have an exclamation mark after the number in the statistics, does this mean that I can choose to fire any amount of shots (1-13) the weapon is capable of?

Or does RoF 9/13 should actually be 9/13! ?

I do not have a working knowledge of guns, I never fired an LMG or any other weapon on fully automatic mode.

There are LMGs in High Tech that lack a ! after it's RoF, then there are also SMGs that have a ! after it's RoF. So I just don't get it. Does an FN MINIMI prevent it's user to fire a single shot with it, cause it doesn't have a single shot selector? Or because a mechanical limitation prevents the user to just pull the trigger that short? Which in turn makes sense when looking at the GE M134 with RoF 33!/66! where the limitation could be the human reaction time?

And if you actually can fire 1-13 shots with an MP5 on full-auto, why would you ever select a different firemode from full-auto? How would the Perk "Lightning Fingers" matter - besides from being able to turn the switch from safe to full-auto?

Please explain.

Cheers!

Onkl
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Old 01-19-2017, 02:22 PM   #2
johndallman
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Default Re: Rate of Fire with selective fire weapons

Quote:
Originally Posted by Onkl View Post
It has RoF 9/13 (HT123), meaning that it has a selector which enables the operator to select single shot fire (RoF 3 without the Fast-Firing technique), burst mode (RoF 9, firing 3 bursts in short succession), and full automatic (RoF 13).
OK so far.
Quote:
Since the full automatic mode does not have an exclamation mark after the number in the statistics, does this mean that I can choose to fire any amount of shots (1-13) the weapon is capable of?
In theory, yes. In practice, a GM is entitled to ask you to make some kind of roll to fire the exact number you want. Using separate trigger pulls for bursts of 3 is easier to do under stress, and thus more reliable in action.
Quote:
There are LMGs in High Tech that lack a ! after it's RoF, then there are also SMGs that have a ! after it's RoF.
There are LMGs that can be fired with single shots, their selectors are safe, single and full-auto. There are also SMGs that have only safe and full-auto.
Quote:
Does an FN MINIMI prevent it's user to fire a single shot with it, cause it doesn't have a single shot selector? Or because a mechanical limitation prevents the user to just pull the trigger that short?
Probably the former. The general GURPS rule for RoF! weapons (B.270) is that the minimum burst size you can manage by trigger manipulation is 1/4 the RoF, although that's subject to override by individual weapon descriptions. The description in High-Tech doesn't say anything about it. A little web searching reveals that the gun has a two-position safety, with Safe and Fire positions, so it seems there's no way to fire single shots.
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Old 01-19-2017, 02:35 PM   #3
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Default Re: Rate of Fire with selective fire weapons

Quote:
Originally Posted by Onkl View Post
Hi guys

...

And if you actually can fire 1-13 shots with an MP5 on full-auto, why would you ever select a different firemode from full-auto? How would the Perk "Lightning Fingers" matter - besides from being able to turn the switch from safe to full-auto?

Please explain.

Cheers!

Onkl
I don't have the book you're getting a lot of this from (like "Lightning Fingers"), so I don't know how to respond to that. BUT... I can respond to why you would use lower rates of fire.

Think about the Rcl number. Each shot requires an additional amount of margin of success to hit the target. If you have 13 shots and Rcl of even 1, that means you'd need to hit by a margin of 12 for all the shots to hit. If you consider range penalties too, that quickly becomes very unlikely. And that matches the real world too. Hitting a target with all the rounds in the stream of bullets is really hard. So full auto is not very good if you've got a specific target. It's mostly useful for suppression fire.

On top of not being likely to hit will even half the rounds, it tears through ammo really fast. And ammo is heavy, so even if you can reload fast, it doesn't make a lot of sense to spend that much of your ammo per second.

Three rounds per second is going to get you the best return on investment. You're much likelier to hit with the rounds you shoot, and you still get damage from multiple rounds.

I'm pretty sure real world soldiers think this way too.
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Old 01-19-2017, 03:45 PM   #4
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Default Re: Rate of Fire with selective fire weapons

I'd probably apply the ! effects to any use of a selective fire weapon set to full auto.
Quote:
Originally Posted by kdtipa View Post
I don't have the book you're getting a lot of this from (like "Lightning Fingers"), so I don't know how to respond to that. BUT... I can respond to why you would use lower rates of fire.

Think about the Rcl number. Each shot requires an additional amount of margin of success to hit the target. If you have 13 shots and Rcl of even 1, that means you'd need to hit by a margin of 12 for all the shots to hit. If you consider range penalties too, that quickly becomes very unlikely. And that matches the real world too. Hitting a target with all the rounds in the stream of bullets is really hard. So full auto is not very good if you've got a specific target. It's mostly useful for suppression fire.

On top of not being likely to hit will even half the rounds, it tears through ammo really fast. And ammo is heavy, so even if you can reload fast, it doesn't make a lot of sense to spend that much of your ammo per second.

Three rounds per second is going to get you the best return on investment. You're much likelier to hit with the rounds you shoot, and you still get damage from multiple rounds.

I'm pretty sure real world soldiers think this way too.
The question asked was not why to fire fewer rounds, it was why to fire on any setting other than full-auto. You can fire full-auto without firing all RoF rounds.

...Also, 3 rounds is not a particularly good number. One is good, two has points for it, and 5+ for the bonuses can be useful, but 3 seems pretty bad.
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Old 01-19-2017, 07:01 PM   #5
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Default Re: Rate of Fire with selective fire weapons

Quote:
Originally Posted by Ulzgoroth View Post
...Also, 3 rounds is not a particularly good number. One is good, two has points for it, and 5+ for the bonuses can be useful, but 3 seems pretty bad.
Actually exactly 3 rounds is surprisingly often the right number to shoot with a rcl 2 weapon at close range. Specially something like a SMG with not very high damage and jet many shots. With such a weapon chasing an extra hit at 6-/7- is often worthwhile so at effective skill 10-11 that 3 shots is what I have used i games and extremely often the actual to hit number has been about that. With a carbine type weapon the third hit is slightly less worthwhile to hunt as two hits is more likely to be enough so the with to conserve ammo reduces such occasionally.
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Old 01-19-2017, 08:11 PM   #6
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Default Re: Rate of Fire with selective fire weapons

Quote:
Originally Posted by Onkl
Hi guys

I am currently trying to understand Tactical Shooting, having played a few test rounds with friends, a question about Rate of Fire and full automatic mode came up.

Let's take the MP5A5 as an example.

It has RoF 9/13 (HT123), meaning that it has a selector which enables the operator to select single shot fire (RoF 3 without the Fast-Firing technique), burst mode (RoF 9, firing 3 bursts in short succession), and full automatic (RoF 13).

Since the full automatic mode does not have an exclamation mark after the number in the statistics, does this mean that I can choose to fire any amount of shots (1-13) the weapon is capable of?

Or does RoF 9/13 should actually be 9/13! ?

I do not have a working knowledge of guns, I never fired an LMG or any other weapon on fully automatic mode.

There are LMGs in High Tech that lack a ! after it's RoF, then there are also SMGs that have a ! after it's RoF. So, I just don't get it. Does an FN MINIMI prevent its user firing a single shot with it, because it doesn't have a single shot selector? Or because a mechanical limitation prevents the user to just pull the trigger that short? Which in turn makes sense when looking at the GE M134 with RoF 33!/66! where the limitation could be the human reaction time?

And if you actually can fire 1-13 shots with an MP5 on full-auto, why would you ever select a different firing mode from full-auto? How would the Perk "Lightning Fingers" matter - besides from being able to turn the switch from safe to full-auto?

Please explain.

Cheers!
First, I don’t have High Tech for GURPS, 4th Ed or Tactical Shooting, so I can’t be of much help in terms of current rules usage but I have live fired automatic weapons, so I can help explain what it is that the rules are modelling.

Second, I’m assuming your reference to a single shot RoF 3 is actually RoF ~3. The ~3 indicates that is physically possible to fire as many as three shots in succession within one second, not that it is what happens every time. Even with a RoF ~3 weapon such as the FNC1, it is comparatively rare to fire more than one bullet in a single second. Proper breathing and aiming technique comes out closer to firing a single shot once every six seconds for a RoF 1/6 when snap shooting, i.e. using quick but aimed fire.

Now, let’s talk about the FNC1’s big brother, the FNC2. The FNC2, unlike the FNC1, was an automatic rifle. The fire selector switch had three positions, S (Safe, not single shot), F (Fire, the single shot position) and A (Automatic, the fully automatic position) arranged in that order in a lower semi-circle with A being much more distant from F than F was from S, to avoid accidentally selecting A. The trigger is connected to a sear which prevents the weapon from firing unless the trigger is pulled. The mechanical safety (S) setting locks the trigger so it cannot be pulled. What the A setting does is to move the sear from its blocking position. With the sear out of the way, the rifle continues to cycle (fire) as long as the trigger is held down, i.e. you’ve squeezed the trigger until the weapon started firing but did not release the pressure of your finger on trigger thereafter.

Felt recoil from a weapon in full automatic is negligible in terms of kick, instead the weapon will tend to climb if hand held or “walk” forward if mounted on a bipod or tripod. You can feel and hear the individual rounds being fired for fully automatic weapons with low RoFs, basically any magazine-fed weapon, such as machine pistols (presumably the MP5A5 falls in this category), SMGs (the Sten and the Sterling), assault rifles (the M16/C7), automatic rifles (FNC2 and BAR), and LMGs (Bren and Lewis), therefore you can count three rounds and release the trigger. Belt-fed and cassette-fed weapons are a different story, usually having only S and A settings. The usual training is to fire in short bursts (approximately three rounds each) to conserve ammunition. In most instances, automatic fire is used to suppress your opponent, not to kill or incapacitate him. Intermittent bursts are “good enough” to accomplish that goal.

I’ve never fired a weapon that had a burst limiter but burst limiters came into use in my lifetime and there was quite a bit written about them in newspapers and magazines at the time. They were developed late in the War in Vietnam (ca. 1968, IIRC). As I mentioned with fully automatic weapons, the weapon fires until you release the trigger. Soldiers were noted to sometimes keep the trigger depressed until the weapon was empty. This was wasteful of ammunition, if nothing else. Therefore, the U.S. had weapons altered by adding burst limiters. As I understood it, in most instances the burst limiter replaced the fully automatic position. The burst limiter had a ratcheting mechanism that moved with each round fired. Every time the ratchet moved three positions, it re-engaged the sear, meaning the trigger had to be released and squeezed again to resume fire. It was an effort to enforce fire discipline through mechanical means. I believe there were some weapons that had a four-position fire selection switch: S, F, burst (unsure of the symbol), and A.

Now, for why you wouldn’t use A all the time, let me tell you about the first time I fired an FNC2 on the range. What I was supposed to do was engage successive targets with three round bursts and I would be scored for hits achieved. What happened was I pulled the trigger (in A) on the first target and didn’t let go. In roughly two seconds, I had completely emptied my 30-round magazine and missed the first target completely, scoring zero. Under actual battle conditions, I would have been personally defenseless (MPs, SMGs, ARs and LMGs, while technically crew-served, replace your personal weapon. The loader still has his personal weapon.) while I reloaded. (Presumably, I would have had additional loaded magazines or loose rounds to load the magazine with [which would take longer]) Incidentally, I also caught Merry H, E, double hockey sticks for disobeying instructions.

I am hopeful that this explanation clears it up for you.

Last edited by Curmudgeon; 01-19-2017 at 08:21 PM.
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Old 01-19-2017, 08:35 PM   #7
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Default Re: Rate of Fire with selective fire weapons

I was trained to only ever use semi-auto with rifles and fire controlled bursts ("Die, M____ F____, die!") with MGs (and the primary purpose of MG fire is suppression).
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Old 01-20-2017, 06:45 AM   #8
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Default Re: Rate of Fire with selective fire weapons

Quote:
Originally Posted by Ulzgoroth View Post
The question asked was not why to fire fewer rounds, it was why to fire on any setting other than full-auto. You can fire full-auto without firing all RoF rounds.

...Also, 3 rounds is not a particularly good number. One is good, two has points for it, and 5+ for the bonuses can be useful, but 3 seems pretty bad.
I apologize for misunderstanding the question. I expect that in real life, you avoid full auto because you don't want to have to rely on twitchy things like how long you hold the trigger to control your ammo usage, and perhaps to avoid things like having to keep your wits about you when someone is shooting back at you to make sure you don't just squeeze out of fear and waste all your ammo.

I guess if there are rules for controlling your rate of fire even in full auto, then maybe there's no reason in game to avoid full auto. I just know that in reality, it's smart to avoid using full auto as it tends to lead to waste without any real benefit.

As for 3 shots vs 2 shots per round being the ideal? I suspect it's dependent on situation. If my target is wearing any armor at all, and I'm close enough to be pretty confident I can hit with 3, I'd go with three just to get the extra potential damage. If I'm further away or the target is completely unarmored, I might slow down to two shots per second.
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Old 01-20-2017, 07:21 AM   #9
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Default Re: Rate of Fire with selective fire weapons

Quote:
Originally Posted by Onkl View Post
Since the full automatic mode does not have an exclamation mark after the number in the statistics, does this mean that I can choose to fire any amount of shots (1-13) the weapon is capable of?
Yes. That is how it works in real life, and that is what it means in GURPS.

Quote:
Originally Posted by Onkl View Post
Or does RoF 9/13 should actually be 9/13! ?
No, since the ! notation means that there is no single-shot setting.

Now, realistically you can tap the trigger and try to coax only single shots out of a gun that is set on full-auto. That's fairly easy if the RoF is low, and difficult if it is high, and probably impossible if it is very high. Most trained machine gunners can fire short bursts of 2-3 rounds even on full-auto with a RoF 10-15 weapon. GURPS uses the generic rule of 1/4 of RoF (p. B270) to model this, but I'd let any shooter with superior skill (say, 16+) or the Lightning Fingers perk ignore that.

Quote:
Originally Posted by Onkl View Post
Does an FN MINIMI prevent it's user to fire a single shot with it, cause it doesn't have a single shot selector?
Yes.

Quote:
Originally Posted by Onkl View Post
Or because a mechanical limitation prevents the user to just pull the trigger that short? Which in turn makes sense when looking at the GE M134 with RoF 33!/66! where the limitation could be the human reaction time?
The RoFs of miniguns are probably beyond what you can do with your finger. Also note that miniguns continue to turn for a bit even after they stop firing (wasting ammunition in the process).

Quote:
Originally Posted by Onkl View Post
And if you actually can fire 1-13 shots with an MP5 on full-auto, why would you ever select a different firemode from full-auto?
Some don't. The single-shot setting is mainly a way to ensure that you ALWAYS fire only one shot per trigger squeeze. That's important if you have to account for every shot, like police officers. The 3-round limited burst setting is mainly to ensure that bursts don't run away on you. That's a mental issue that the game doesn't account for.

In the past, quite a few highly trained units have opted to go Full-Auto Always; if single shots were required, they let their fingers do it. The current understanding in most units is to go Semi Always, however, since that ensures the most hits with the least ammunition wasted.

Quote:
Originally Posted by Onkl View Post
How would the Perk "Lightning Fingers" matter - besides from being able to turn the switch from safe to full-auto?
See above. I'd let you ignore the minimum number of shots fired rule of p. B270.

Cheers

HANS
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Old 01-20-2017, 11:21 AM   #10
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Default Re: Rate of Fire with selective fire weapons

Quote:
Originally Posted by kdtipa View Post
As for 3 shots vs 2 shots per round being the ideal? I suspect it's dependent on situation. If my target is wearing any armor at all, and I'm close enough to be pretty confident I can hit with 3, I'd go with three just to get the extra potential damage. If I'm further away or the target is completely unarmored, I might slow down to two shots per second.
It probably does, really...but TBH if you're close enough to be confident you can hit with 3 and actually need the hits I'd be very tempted to go full-auto for the extra hit or two the RoF bonus can let you get. You might burn half a magazine that way but if you're that close you really don't want the target surviving to their next turn.
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