Hand Grenade Fragments and Hits

[Onkl]

Hi guys

As per B415, grenades with a fragmentation hull have a special statistic in [] saying how much damage these fragments will do over what distance. It also says that

Originally Posted by B415

It is possible for several fragments to hit! For every three points by which the attack roll succeeds, one additional fragment strikes the target.

It seems to me, that the farther away from the impact point the lower the chance should be that you are hit. This is also modeled in the rules, as the frags have a skill of 15 to hit which are subject to distance modifiers.

But what about the "recoil" (I just use recoil, as the application of the rule is as recoil with ranged weapons), it is at a flat 3 and does not change.

Wouldn't it be better to have the recoil be dependent on the distance the victim is from the grenades impact?

Have there been any expanded rules concerning fragments I am not aware of? I've checked High Tech, Tactical Shooting, Gun Fu and Ultra Tech but didn't find anything.

It may also be that I am very spoiled by Hollywood and just think that frag grenades are much more effective that they are in real life.

If you had or have any ideas, please let me know.

Cheers

Onkl

[johndallman]

Looking at the hand grenades in High-Tech, they range up to [3d], which means a maximum range of 15 yards, which is a range penalty of -5. The "attack skill" at that range is 10, with for a 50% chance of a hit, a 16.2% chance of two, and a 1.9% of three.

At 2 yards range, there's a 95% chance of one hit, a 74% chance of two, and 37.5% of three.

Most grenades do 2d cutting on an unarmoured human per hit. That's an average of 10.5 points of wounding, which is a "that's enough for today" wound for most people who aren't being excessively heroic, from a single hit.

This seems adequately dangerous for their military purpose. The impression I have of fragmentation grenades is that they are very dangerous at close range, but become less so quite rapidly at distance, due to the inverse square law. The rules seem to fit this model.

[Ulzgoroth]

Originally Posted by Onkl

But what about the "recoil" (I just use recoil, as the application of the rule is as recoil with ranged weapons), it is at a flat 3 and does not change.

Wouldn't it be better to have the recoil be dependent on the distance the victim is from the grenades impact?

That never, ever happens in the regular autofire rules that the frag rule is imitating. Why would you do it with fragments?

Originally Posted by Onkl

It may also be that I am very spoiled by Hollywood and just think that frag grenades are much more effective that they are in real life.

...I'm curious which movies make frag grenades look impressive. Most of what I see is 'do not touch the fireball' explosions and doesn't really depict fragmentation at all.

[Bruno]

My experience with fragmentation in GURPS is that it's plenty dangerous, even without the usual "kaboom". Using the Shattershot Imbuement, or spells with houseruled-on fragmentation, we've found that even with body armor getting fragged is an issue.

We've actually found that for most light-fantasy-combat-scale explosions, the fragmentation is the worst part. It doesn't suffer a damage penalty from range!

[Phoenix_Dragon]

Originally Posted by Onkl

But what about the "recoil" (I just use recoil, as the application of the rule is as recoil with ranged weapons), it is at a flat 3 and does not change.

Wouldn't it be better to have the recoil be dependent on the distance the victim is from the grenades impact?

I'd say no. Due to the range penalties and the natural bell-curve produced by 3d6 rolls, the chance of multiple hits drops sharply with range. Increasing recoil for range would be some harsh double-dipping, especially if it applies to other ranged attacks as well (And makes even less sense if they end up using different mechanics).

[Varyon]

Trying to do grenades "correctly" would be a pain. Let's consider the M67, which has a convenient casualty radius of 15 meters, which we'll round down to 15 yards. "Casualty radius" means something like "50% of targets at this range will become casualties" - that is, you can expect 50% of people (SM+0 targets) that are 15 yards away (-5 to hit) to be hit by at least one fragment. We'll call that an average of 0.5 fragments. Assuming the fragments spread in a mostly-uniform pattern, that would mean at 10 yards out (-4 to hit) you'd expect an average of a bit over 1.5 fragments. At 7 yards (-3 to hit), you'd expect around 4 fragments. At 5 yards (-2 to hit), that's 13.5 fragments. At 3 yards (-1 to hit), that's 62.5 fragments. At 2 yards (+0 to hit), that's 171.5 fragments.

Yeah. You try to turn that into something gameable. You've also got to try to figure out how many fragments a grenade actually makes to get an idea of what the cap is - the above scheme works out to roughly 1500 fragments total (human profile is roughly 1 square yard, fragment density at 15 yard radius is roughly 0.5 fragments per person, or 0.5 fragments per square yard, and the surface area of a 15 yard radius sphere is a bit shy of 3000 square yards).

[Kazander]

Originally Posted by Bruno

My experience with fragmentation in GURPS is that it's plenty dangerous, even without the usual "kaboom". Using the Shattershot Imbuement, or spells with houseruled-on fragmentation, we've found that even with body armor getting fragged is an issue.

We've actually found that for most light-fantasy-combat-scale explosions, the fragmentation is the worst part. It doesn't suffer a damage penalty from range!

Ditto.

Also, I hate the Fragmentation rules. Not because they're bad, but because they're slow. Combat grinds to a halt when the Wiz tosses a Shattershot. And it's disproportionately effective, because of the lack of a damage penalty, because of random hit location, and because it's easy to metagame and declare the shot lands just beyond the range where the players can be affected. Downside of playing on a hex-grid.

[Varyon]

I just wrote up a nice system with reasoning, and the forum ate it, so here's the Cliff notes:

Frag	Range		Skill	NKR	NCR
[1d]	5/20		13	1.5	5
[1d+2]	7/30		14	3	7
[2d]	10/50		15	5	15
[3d]	15/70		16	15	20
[5d]	20/100		17	20	30
[7d]	30/150		18	50	50
[10d]	50/200		19	70	70
[15d]	70/300		20	100	100
[20d]	100/500		21	150	150

Rcl is 3 in all cases. NKR is nominal kill radius (50% of targets take 3d or more damage), NCR is nominal casualty radius (50% of targets take 1d or more damage). Fragments attack with skill based on dice of fragmentation, Range includes a 1/2D and Max (hence the two number designation), and being closer than 2 yards gives a to hit bonus - +2 for 1 yard, +4 for range C. Contact explosions are at +4 and have a minimum of 1 hit, internal are also at +4 but with a minimum of 4 hits. Those on the opposite side of a target hit with a contact explosion get his Cover DR against the fragments; for internal explosions, all targets get half this value.

If you want to speed things up, instead of rolling 3d for each target and damage for each hit, roll damage first (same for each hit, halved beyond 1/2D) then just roll 2d. After that, roll 1d for each target, adding this to the previous 2d roll to see if you score a hit. So, for a [3d] that explodes in the middle of a group of 7 people - two 1 yard from the epicenter, one 3 yards out, two 5 yards out, one 10 yards out, and one 20 yards out, you'd do the following: Roll 3d for damage; you get an 8. Next, roll 2d - a result of 9. Roll 1d for each target - 6, 3, 2, 4, 1, 5, 1, for 15, 12, 11, 13, 10, 14, 11, respectively. With base skill 16, target numbers are 18, 18, 15, 14, 14, 12, 10, respectively. That's 2 hits (16 damage), 3 hits (24), 2 hits, 1 hit (8), 2 hits, 0 hits (0), and 1 hit (4 - beyond 1/2D), respectively. Assuming no armor, that's 24 injury, 36 injury, 24 injury, 12 injury, 24 injury, 0 injury, and 6 injury - yowch.


EDIT: These numbers are based on the kill radius of the M67 being 5 meters (rounded down to 5 yards) and the casualty radius being 15 meters (rounded down to 15 yards). The M67 is [2d] in GURPS; the rest are extrapolated from here. Max was chosen to correspond to skill 7, below which you're basically crit-fishing and rolling isn't worthwhile.

[mook]

In a post about grenades, I made a quick chart of common grenades with their damage and 'skill' level pre-figured. Might be of some use. Also, the GURPS Calculator has a tool for explosives.

Generally, if I don't have one of those resources handy, I just "eyeball" things and keep it moving.

[Fred Brackin]

Note that the entire Gurps fragmentation system is grossly unrealistic. WWI helmets as low as DR3 were considered "effective" (whatever that means) against fragments from large artillery shells. Same for WWII to 1980s vests of DR4 to 5 even when it was acknowledged that they did little good against bullets.

So while fragments do little damage individually the number that hits is from a hand grenade explosion within the casualty radius in the in the high tens to even hundreds. You can see this by counting the number of hits that fail to penetrate a sheet of plywood.

Then there are things like the ball bearings in a claymore or newer grenades like the Diehl that can not reasonably be described as "cutting".

A system that was even real-ish could be much more complicated but even a simpler one assigning an automatic number of hits at a penetration of 1D(0.5) at a given distance would be at least as good a playable abstraction.