Grenades and Fuses -- Variable or Determined?

[mook]

Howdy Folks!

Had a discussion on the unofficial Discord but still not sure I'm clear regarding the Fuse entry for grenades. Please note that I'm curious about the rules mechanics and the intent of the values given, not necessarily what is "realistic" or not (which is easily its own conversation).

So, p. 277 of "Characters" establishes the Fuse entry as "...the number of seconds it takes for the weapon to detonate once readied."

So far, so good. All of the entries in the Hand Grenade table have discreet fuses, so a TL6 frag grenade explodes 4 seconds after being readied, a TL 8 stun grenade 2 seconds after being readied, etc.

Except one, which is where I start to lose my way.

School me, hivemind!

The TL 5 black powder grenade has a Fuse of 3-5, and the notes for it indicate "...a blackpowder grenade detonates 3-5 seconds later, depending on fuse length."

To me, that means "set the fuse at 3, 4, or 5 seconds," but I quickly discovered that is not universal consensus and that many GMs read it as "roll randomly to determine a number of seconds from 3 to 5."

So... which way do you play it?


I mostly keep myself to the Basic Set, but if we expand into High-Tech a bit, the modern grenades no longer have discreet Fuse entries but have rather been expanded to "4-5" (p. 192), and p. 190 adds "Veteran fighters often 'cook off' a hand grenade by letting the arming handle fly off, taking two Wait maneuvers, and then throwing the weapon. With a four-second fuse, this leaves no time for a defender to pick it up and throw it back."

I note there is no grenade listed with a Fuse of simply "4," so again to me a "four-second fuse" would mean "a Fuse of 4-5 set to 4." Or is it supposed to mean "A Fuse of 4-5 which, when randomly rolled, came up as 4"?

[johndallman]

Originally Posted by mook

The TL 5 black powder grenade has a Fuse of 3-5, and the notes for it indicate "...a blackpowder grenade detonates 3-5 seconds later, depending on fuse length."

To me, that means "set the fuse at 3, 4, or 5 seconds," but I quickly discovered that is not universal consensus and that many GMs read it as "roll randomly to determine a number of seconds from 3 to 5."

So... which way do you play it?

For TL4-5 grenades, I'd definitely roll. As High-Tech p. 190 says, grenadiers prepare their own grenades, which involves filling them with powder, cutting a length of fuse, and inserting it. They then have to light the fuse before use, and with TL-4-5 means of ignition, there's scope for variation in the time that takes. The fuse also doesn't burn at a terribly consistent rate.

I'd let a character change their intended fuse interval with a roll against Explosives/TL (any at TL4-5), simply by cutting a longer or shorter fuse; this would be more reliable if they could make trials with fuse off the same coil as they used in action. But they'd still have +/- 1 second on the delay, without a really good excuse. Rain, of course, messes this up, if you can get the fuses to work at all.

I mostly keep myself to the Basic Set, but if we expand into High-Tech a bit, the modern grenades no longer have discreet Fuse entries but have rather been expanded to "4-5" (p. 192), and p. 190 adds "Veteran fighters often 'cook off' a hand grenade by letting the arming handle fly off, taking two Wait maneuvers, and then throwing the weapon. With a four-second fuse, this leaves no time for a defender to pick it up and throw it back."

I note there is no grenade listed with a Fuse of simply "4," so again to me a "four-second fuse" would mean "a Fuse of 4-5 set to 4." Or is it supposed to mean "A Fuse of 4-5 which, when randomly rolled, came up as 4"?

TL6-7 grenade fuses do not have switches or other controls to set different times. The delay is normally something that burns at a fairly predictable rate, which is ignited by a percussion cap when you let go of the arming handle. There is one grenade with a fuse of 4 in High-Tech: the Mills Number 36M's description has an alternative 4-second fuse available from 1940.

Now, Mills Bombs were pretty cheaply made, and not technologically unusual, so it would seem a bit odd if their fuses had less variance than other grenades. The 4 and 7 second fuses were definitely separate components, you picked one to use when you primed the grenade before combat. But it would be really weird if most of the grenades in High-Tech were issued with two fuses with only a second difference in length.

So I think you need to roll for the TL6-7 grenades with fuses like "4-5". The basic technology didn't support selection of delay just before throwing.

[RyanW]

Originally Posted by mook

I note there is no grenade listed with a Fuse of simply "4," so again to me a "four-second fuse" would mean "a Fuse of 4-5 set to 4." Or is it supposed to mean "A Fuse of 4-5 which, when randomly rolled, came up as 4"?

Fuses were unreliable, and were variable to a small (or sometime large) degree. There was a batch of captured Japanese grenades found to have effectively zero delay, though whether that was a production error or a batch meant specifically for booby traps is debated.

[Fred Brackin]

Originally Posted by johndallman

TL6-7 grenade fuses do not have switches or other controls to set different times. The delay is normally something that burns at a fairly predictable rate, which is ignited by a percussion cap when you let go of the arming handle.

TL6-7 grenades still have fuses that were cut by hand. They were just cut at the factory and are not accessible to the user.

I'd say that anywhere fuse length is given as a variable length random determination is the thing to do.

[Varyon]

The "depending on fuse length" indicates to me that the intent was that you set how long it takes when initially fusing the grenade, by literally using a shorter or longer fuse. For PC's who lack Demolitions, this is probably set when they purchase or are issued the grenades. If the intent were for the GM to randomly determine this, that would most likely have been mentioned somewhere in the text. Now, low-TL grenades having some variability in when they go off would make sense, although it's possible the authors considered that to simply be part of their worse Malf value.

[Fred Brackin]

Originally Posted by Varyon

T If the intent were for the GM to randomly determine this, that would most likely have been mentioned somewhere in the text.

I do not believe HT was written in this gamist/prescriptive fashion. It's sections dealing with real gear from the real world report the facts as best as they can be determined.

So if it says that some hisotorical grenade had a fuse length of 4-5 seconds I believe it means a variable time ranging from 4 seconds to 5 seconds was the historical fact.

[Varyon]

Originally Posted by Fred Brackin

I do not believe HT was written in this gamist/prescriptive fashion. It's sections dealing with real gear from the real world report the facts as best as they can be determined.

So if it says that some hisotorical grenade had a fuse length of 4-5 seconds I believe it means a variable time ranging from 4 seconds to 5 seconds was the historical fact.

HT was written to be used in a game. It would be a pretty serious oversight to leave out the whole "the GM randomly determines how long the grenade lasts before exploding" thing if that were the intent (and reading the section on grenades, there's no mention of unreliable fuse times). It's certainly a possibility, but GURPS products are usually written to a higher standard than that. Additionally, HT's grenade table refers back to the grenade table from Basic for an explanation of the columns, and there the only variable-length fuse grenade (the TL3 Black Powder) explicitly states the amount of time it takes depends on fuse length, with no mention of a random roll.

Note also that the poor Malf of low-tech grenades also sort of already covers this. On a malfunction, a roll of 3-4 means it explodes 1d seconds late, while a roll of 15-18 means it explodes early (well, immediately, but close enough).

All that said, treating it as variable length certainly is an option, and may be more realistic, but I don't have any reason to believe this was the intent. If you want super gritty, feel free to make it variable (and it shouldn't be a full multiple of seconds; another random roll to determine what initiative count it explodes on is appropriate).

[Fred Brackin]

Originally Posted by Varyon

HT was written to be used in a game.

It was written to provide good information for use in a game. If grenades came from the factory with unreliable fuse lengths that's a historical fact and is how HT should list them.

[malloyd]

Originally Posted by mook

I note there is no grenade listed with a Fuse of simply "4," so again to me a "four-second fuse" would mean "a Fuse of 4-5 set to 4." Or is it supposed to mean "A Fuse of 4-5 which, when randomly rolled, came up as 4"?

Grenades definitely don't have a variable timer you can set. In theory you could probably design one, but do you really want to add all the extra failure modes of a complicated trigger mechanism to a bomb you are carrying around with you? The TL5 ones may be adjustable in that they have a length of fuse you can cut to a shorter length, but anything modern the fuse is fully enclosed and you can't mess with it - the delay is set when it's assembled.

And yes, it realistically is variable - it's how long it takes for a small length of something to burn, and that's not a process easily standardized to a fraction of a second. People who hold grenades for them to "cook off" are generally called "idiots" not "veterans", and get a lecture and a punishment detail if they survive. Yes there are times troops might try it for some particular purpose, but no service is ever going to *recommend* it.

Realistically a 4 second delay isn't long enough for the grenade to land with enough time on the fuse to pick it back up and throw it back anyway (keep in mind real thrown objects don't travel *instantly*, there's a flight time that's abstracted away for rules purposes). This was something that happened with grenades in World War I, and is part of the historical reason the delay was reduced to 4 seconds from the closer to 10 seconds it was in those earlier designs.

[mook]

Thanks all, Varyon in particular -- I don't really care about "realism" here (else I'd just do my own research and house rules), I was really just curious if I'm the only one who uses the grenade Fuse value as-written (kind of sounds like I am lol).