*GURPSDay* has again descended in all its glory! Enjoy the weekly heaping helping of GURPSy goodness.

Today’s topic here on Game Geekery, like last week’s discussion of shotguns, is another GURPS “fiddly bit” — explosions, specifically grenades.

While the rules governing explosions aren’t *terribly* complex, they can require some quick math if you’ve not already figured everything and written it on the character sheet of whoever is flinging that little ball of death. I’ve created a handy PDF table of the damaging grenades from the Basic Set, extrapolating both their blast and fragmentation damages (and attack number) out to a range of 16 yards. The examples below might be clearer if you download and follow along:

**GURPS Grenades Table** | **Downloads: **803 | **Size: **113.8 KB

Grenades like Molotov cocktails and smoke/gas grenades don’t actually *explode*, so the rules for those are just like any other Area-Effect attack (p. 413).

For damaging grenades, you can find all the relevant rules in the *Basic Set* on pp. 414-415, and the stats for the actual grenades on p. 277. Naturally, this being GURPS, those rules are *greatly* expanded in *Low-Tech* (pp. 84-86), *High-Tech *(pp. 181-196), and *Ultra-Tech* (pp. 146-147), depending on what TLs your games include. But they all follow basically the same rules, so I’m limiting this post to the core books.

Okay, so your character has a grenade in hand and has pulled the pin, intent on ruining the day of some poor bad guy. You have two choices:

**Target the Enemy Himself**

If you do this, roll against your Throwing skill (or the default of DX-3, or your Dropping skill if you happen to be flying). If you fail, your margin of failure is how many yards off the throw was (to a maximum of half the distance to target), with direction rolled randomly (p. 414). If you succeed and the target doesn’t dodge, congratulations, he is now the dead center of the explosion and will likely be very unhappy. If you succeed but the target dodges, *his *margin of success determines how many yards off the throw was (direction still rolled randomly).

So, assuming a target with a Dodge of 11 standing 10 yards away (-4 on the Range table, p. 550; failed attacks cannot go further than 5 yards away from the intended target) and a Throwing skill of 15 (effectively 11, due to range), some examples:

**Failure:**You roll a 14, missing by 3. The grenade lands 3 yards away from the target, direction determined by 1d**Success:**You roll a 10, succeeding by 1. The grenade hits your target directly and explodes where he stands**Dodged Success:**You roll an 11 and succeed, but the target rolls a 10 to dodge. The grenade lands 1 yard away from the target, direction determined by 1d

**Target the Enemy’s Hex**

Or, instead of trying to hit the enemy, try to land the grenade in the hex he is standing in. The advantages of this is that it gives you a +4 to hit, and the ground can’t make a Dodge roll. The best your target can hope for is to dive for cover (p. 377) to put at least one more hex between the explosion and himself (or get behind cover if there is any close enough). The only only drawback is that if using a fragmentation grenade, a target inside the blast hex isn’t hit automatically by fragments — you need to roll to hit (see below).

If you succeed on your Throwing roll, the grenade lands on the hex you were aiming for; if you fail, your margin of failure is still how many yards off the throw was (to a maximum of half the distance to target), with direction rolled randomly.

Again assuming a target hex 10 yards away (-4 on the Range table, p. 550; failed attacks cannot go further than 5 yards away from the intended target) and a Throwing skill of 15 (effectively 15, as the -4 due to range and the +4 for targeting a hex cancel one another out), some examples:

**Failure:**You roll a 16, missing by 1. The grenade lands 1 yard away from the target hex, direction determined by 1d**Success:**You roll a 12, succeeding by 3. The grenade hits the target hex directly and explodes there

And that’s that — lobbing a grenade at someone is mostly just like any other ranged attack.

Once we know what hex is the center of the explosion, we just need to determine how much damage the explosion does to each target affected.

The *Basic Set* damaging grenades fall into two categories: those with fragmentation damage (Black Powder and Fragmentation grenades) and those without (Concussion and Plasma grenades). We’ll look at those without fragmentation damage first — they’re the most straightforward.

**Without Fragmentation**

The blast from any grenade (with or without fragmentation) inflicts the damage listed on p. 277 *only* in the hex it actually explodes in. It drops off quickly from there, dividing the total damage by 3 x the number of hexes distance from the blast.

So, using the TL7 Concussion Grenade as an example, let’s say our target is three hexes from the blast center when it explodes. Looking at the PDF table above (or just doing the math), the damage given is “(5dx2)/9.” Rolling 5d gives us, say, a total of 18, multiplied by 2 is 36, and divided by 9 leaves only 4 points of injury. This would be 6 points of injury at two hexes away (36/6), 12 points at one hex away (36/3), and 36 points in the “ground zero” hex itself.

**With Fragmentation**

The only difference when using grenades with fragmentation damage is, they inflict *two* kinds of damage — the blast, as above, and then additional fragmentation damage, given in brackets on the weapons table. So, damage of “4d cr ex [2d]” is 4d blast damage and 2d fragmentation damage; “8d cr ex [3d]” is 8d blast damage and 3d fragmentation damage; etc.

This fragmentation damage is expressed as an attack made at skill level 15 — it only hits automatically if you actually strike the target with the grenade (not just the hex he is standing in). This attack uses standard range penalties (as well as target’s Size Modifier and posture), and can hit with more than one piece of shrapnel (p. 415).

Here’s an example against multiple targets, using a TL 7 fragmentation grenade. (Note that a grenade like this has the potential to inflict damage out to 16 yards away from its blast, so the thrower will want to either be further away than that, or behind cover. An average person with ST 10 can throw a 1-pound grenade up to 35 yards — see “Throwing Distance,” p. 355).

**A:** K-9 handler, no armor, 4 yards from blast center (-2 range penalty to hit)

**B:** Bomb sniffing dog, no armor, SM -2, 3 yards from blast center (-1 range penalty to hit)

**C:** Sentry, armor DR 2, 2 yards from blast center, kneeling down to read map (0 range penalty to hit, -2 to be hit by fragmentation)

**D:** Sentry, armor DR 2, 4 yards from blast center, 1 yard from low (waist-high) stone wall (-2 range penalty to hit)

The attacker is 20 yards “off-screen,” to the left, and is trying to land a grenade in the hex marked “X.” He has a Throwing skill of 15, a +4 bonus for attacking a hex of ground, and a -6 penalty for range, for an effective skill of 13. He throws the grenade and rolls a 15, missing by 2. He rolls an additional 1d and gets a 3, so the grenade actually lands 2 yards away from his target, in the red hex. Sentry **D** shouts “Grenade!” as it lobs through the air (the GM might ask for a Perception roll if this is an unexpected attack, but let’s assume for illustration that all the enemies know there’s an incoming grenade).

The three human targets roll against their Dodge of 10 to “dive for cover.” **A **and **C** both fail with an 11 and 13, but **D** succeeds with an 8… he is prone behind the stone wall when the grenade explodes, and will take no damage.

We first figure damage from the blast. According to the PDF table/basic math, **A** will take 8d/12, **B** will take 8d/9, and **C** will take 8d/6. Rolling 8d for damage, we get a total of 35. **A** has no armor, and takes 35/12 = 2 points of injury; **B** has no armor and takes 35/9 = 3 points of injury; **C** has armor with DR 2 and takes 35/6 = 5 points, minus DR of 2 leaves 3 points of injury.

We then calculate damage from the fragmentation. According to the PDF table/range penalties, our attack against **A** is at -2, so 13. A roll of 11 indicates one piece of shrapnel hits, inflicting 3d cutting damage. The damage roll is 12, x 1.5 (for cutting) = 18 points of injury. He is almost certainly out of the fight (making HT rolls to stay conscious, possibly to stay alive).

Our attack against **B** is at -1 for range and -2 for SM, so 12. A roll of 14 means no fragments hit — Yay, Fido lives!

Our attack against **C** is at 0 range penalty, but -2 because he is kneeling down, so 13. A roll of 9 indicates *two* shrapnel hits (one for success, one for every success by three, p. 415). The first damage roll of 3d6 is 13, minus DR of 2, leaves 11 points of penetrating damage, x 1.5 for cutting = 15 points of injury. The second damage roll is 10, minus DR of 2, leaves 8 points of penetrating damage, x 1.5 for cutting = 12 points of injury. As he has taken a total of 30 points of injury (3 from the blast, 27 from fragmentation), **C** is probably dead, dead, dead (or will be very soon).

As you can see, grenades — especially frag grenades — can be *deadly*. I imagine that’s why most PCs love them so much! (At least, when they’re not on the receiving end).

I hope you found these examples helpful, and please remember the “peanut butter and jelly sandwich” rule… that is, it takes ten times as long to read about making a sandwich as it does to actually do it. Explosions, particularly against multiple targets, do take a bit of figuring, but not so much that it should scare off most groups. The PDF table above should help speed things up, and I’d also recommend just rolling damage a single time and applying the result to multiple opponents (I rolled individually in the example to increase the variety of results).

Like shotguns, grenades can easily be added to the PCs’ arsenal of “ways to kill it, kill it all, and kill it now.”

### “Close only counts in horseshoes and hand grenades.”

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Hey, loved your shotguns breakdown, but I gotta point out one thing about your grenade table: it doesn’t count the multiplied damage dice into account for blast radius. The example on p. B414 states that 6d×2(=12d) affects up to 24 yards (correctly), rather than 12 yards as the plasma grenade (6d×4)(=48d) as the table states (incorrectly).

I don’t mean to come off sounding like a rules lawyer, but higher TL grenades should have bigger explosions. Of course, after a certain distance from the center, the damage becomes nearly negligible anyway, but frag can still be deadly. My 2 cents.

Cheers!

Hi Ben! The whole point of this blog is to be a “rules lawyer” (but in the good way), so never worry about that. 🙂

Thanks for pointing that out. I’ve always thought “everyone within 24 yards is vulnerable…” meant ‘diameter’ (like, 12 yards on either side of the blast center), not ‘radius’, but the way you’re explaining it makes just as much sense, if not moreso.

I’ll check this out on the forums later, and update if needed. Appreciate the heads up!

Thanks for the correction, Ben! The PDF has been updated and expanded.

Great work on this!

I actually made a tool to help with this on gCalc awhile back. Let me know if it lives up to your standards. 🙂

http://gurpscalculator.com/demolition

Hiya, Jeffrey! You know I love gCalc 😀

I looked at that page before I posted this, but I couldn’t find a simple way of determining the things this table does, i.e., “I’m using a TL7 fragmentation grenade, how many hexes am I gonna affect for how much damage.” Am I not using the page right? Or is that maybe something you could add? (You know, in all your copious free time :P)

P.S. Oh, hey, is that “Improvement by Study” page new? I don’t remember that one… Nice!

Argh! I just spent a couple weeks putting together a guide on this exact subject! Somehow in my searching for answers that lead up to said article, your blog here just didn’t come up with my keywords.

Good work! I guess that means there’s two guides out there, at least…suppose this means I can skip the illustrated follow-up!

M.

Hehe, all good Michael, I saw your post and quite liked it. There is indeed an army of GURPS bloggers, but I’ve yet to see any kind of “turf war” over posts. After all, it’s not just the topic, it’s how you, specifically, cover it.

I say keep on blogging what you want to. The rest of us are. 🙂