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Rules for Grenade Launchers
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CRMcNeill
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PostPosted: Fri Jul 28, 2017 9:07 pm    Post subject: Rules for Grenade Launchers Reply with quote

So, I'm working on another stat project that involves light support weapons, including grenade launchers. One of the obvious advantages of grenade launchers is their ability to fire ballistically, lofting shots over intervening cover.

What I'm thinking as far as a rule is allowing a grenade launcher to reduce a target's Cover modifier based on range, but I'd like some input from those of you who have some experience with the real thing...
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Naaman
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PostPosted: Fri Jul 28, 2017 11:11 pm    Post subject: Reply with quote

Im actually working on this myself. When I'm done, it may be similar to what you come up with, but I'll give you some info that may inform your target result.

First, grenade launchers "can" fire ballistically, but its more accurate to say they must be fired ballistically. If the range to the target is known (within 5 or so meters), then hitting the target boils down to a modified application of basic marksmanship fundamentals. Look up some info on leaf sights to get an idea of wht I mean here.

A grenade launcher that is fired like a point and shoot weapon (such as a blaster), will not launch the round with enough power for it to travel very far. It'll "sink" almost immediately.

Grenades have a safety built in: they are designed to detonate on impact, but will only detonate if they have travelled far enough from the weapon befor impact (it has to do with the striation in the barrel: the grenade will not arm until it has spun at least 14-38 full rotations.... dont ask me why that range of spins.... its proba ly due to a physical limitation of the safety device). In any case, this eliminates the chance of blowing oneself up by hitting a target too close to the shooter.

This may be more detailed than you care for, but airborne grenades are very susceptible to wind. The shooter would need to take wind into account for the longer shots.


HEDP are typically used. These grenades have an armor piercing feature that (supposedly) allows them to punch through tank armor and thus detonate INSIDE the tank (or bunker or whatever). I never put that function to use in real life, so cannot comment on it. If it were my rule, I might allow it to ignore the scale difference when rolling damage against walker scale or smaller targets or some such.

Hopefully Dredwulf or demonapostle will have something to add.


Just ask if any of that needs clarifying.
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Naaman
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PostPosted: Sat Jul 29, 2017 11:45 pm    Post subject: Reply with quote

As for ignoring cover, its a hard call for me to make. "Cover" fully protects against attacks. Concealment is what makes a "hit-able" target harder to hit (cover makes a target impossible to hit).

I'm of the opinion that blast radius weapons should be harder to dodge... assuming the round lands on target. Shooting at a target with "cover" (which usually also provides concealment) means the shooter is guessing about what he is shooting at, more like a mortar than a grenade launcher.

On the other hand, if we are talking about trench warfare or some such, then this may be applicable.
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CRMcNeill
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PostPosted: Sun Jul 30, 2017 3:38 pm    Post subject: Reply with quote

I was looking at Cover reduction as part of the grenade launcher's ability to loft a grenade over an intervening object or terrain feature, since Cover and Concealment are interconnected in the RAW.

It's also worth noting that grenade launchers in a sci-fi setting may have advanced capabilities that negate the limitations of modern equipment. A grenade launcher that functions on a railgun or grav-launcher principle could adjust its muzzle velocities depending on the situation and conditions.

I've been envisioning a system with multi-purpose grenades, ala Aliens, where grenades could either be hand tossed or fired from a grenade launcher. I'm thinking of multiple types of launchers, too: a pump-action under-barrel version, a drum fed version that can fire short bursts, and a tripod-mounted version as a support weapon.
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Naaman
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PostPosted: Sun Jul 30, 2017 5:10 pm    Post subject: Reply with quote

Of course, we have tech that can make even a leaf sight more than accurate enough: a range finder would take all the guess work out of the deal, but I figured that would be reserved for discussion after the baseline rules were worked out.
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nuclearwookiee
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PostPosted: Sun Jul 30, 2017 5:38 pm    Post subject: Reply with quote

Here's a simple (but less realistic) approach. If a grenade is launched instead of thrown, use the range increments of the weapon instead of the throwing ranges of the grenade. Use Missile Weapons instead of Grenade for the skill check. Cover between attacker and target becomes concealment instead, but there could also be cover between the target and the blast point.
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Naaman
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PostPosted: Sun Jul 30, 2017 6:50 pm    Post subject: Reply with quote

I've always interpreted the missile weapons skill as including grenade launchers in the first place.

However, there IS a difference in firing a "point/shoot" missile vs. lobbing a grenade via a launcher. Still, I figure they belong in the same skill group.

Where I run into trouble is in determining how the shooter can "guess" where the target is (how does the GM provide enough information for the player to make a reasonable guess as to the range without giving away the exact distance?)

One way is to have the player roll "missile weapons," and based on that result the GM could say "between x and y meters" giving a narrower range for a higher result (anybody can figure out that a target is more than 10m away or less than a kilometer, etc... but gauging the difference between, say, 80 and 100 meters might be more difficult).
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garhkal
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PostPosted: Mon Jul 31, 2017 3:49 am    Post subject: Reply with quote

Its the same with other games, such as in adnd, does the party know that the enemy is exactly 200 yards away when they first meet, and so can correctly aim their fireball spell out that far?? How, unless they map it out, or know Ranges very well..
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Dredwulf60
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PostPosted: Mon Jul 31, 2017 3:50 am    Post subject: Reply with quote

First of all; full disclosure: my experience with 40mm grenade launchers is minimal.

They were fairly late additions to the Canadian army. (late 1990s) By the time we started to see them, I was a section commander. So I got a brief introduction course, but never carried a launcher.

Having said that, I think you can lob them over general cover...like over a small rise in the terrain, like a berm, but it wouldn't really help much for character level cover. Like a guy hiding behind some boxes, or even in a fighting trench.

If you lob a tennis ball overhead it isn't really going to be that much easier to hit the guy than if you threw it directly at him.

Of course there is the feature of most grenade types: area effect.

But most area effects are line-of-sight from the detonation point.
Intervening cover is going to be a factor unless you land that explosive right on the target.


But: airburst grenades are a thing.
There are those high-tech grenades that airburst at specific ranges...
The guy is hiding in a hole, so you fire the grenade so that it flies right over the hole and detonates exactly above it, depriving the target of his cover.

https://en.wikipedia.org/wiki/XM25_CDTE
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Naaman
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PostPosted: Mon Jul 31, 2017 4:38 am    Post subject: Reply with quote

CRMcNeill wrote:
I was looking at Cover reduction as part of the grenade launcher's ability to loft a grenade over an intervening object or terrain feature, since Cover and Concealment are interconnected in the RAW.

It's also worth noting that grenade launchers in a sci-fi setting may have advanced capabilities that negate the limitations of modern equipment. A grenade launcher that functions on a railgun or grav-launcher principle could adjust its muzzle velocities depending on the situation and conditions.

I've been envisioning a system with multi-purpose grenades, ala Aliens, where grenades could either be hand tossed or fired from a grenade launcher. I'm thinking of multiple types of launchers, too: a pump-action under-barrel version, a drum fed version that can fire short bursts, and a tripod-mounted version as a support weapon.


With regard to the cover/concealment, I guess it's your call. Lobbing the grenade does have its limits: the height of the cover would necessitate firing at a very specific angle in order to clear it, and that same angle could easily cause the grenade to fly too far beyond the target (assuming he is fairly close to his cover... such as that he is using it on purpose, for example).

However, if lobbing the grenades is a regular feature of the weapon, I would tend to make range finders an expensive (or at least a difficult to come by) add-on. Otherwise, I would make lobbing grenades especially difficult, requiring the shooter to accurately gauge the distance to the target or else automatically miss (though I would permit him to "walk" the rounds onto target in appropriate circumstances).

Hmm... concerning the pump action under barrel deal... it sounds cool but comes off as rather impractical unless we're talking about micro grenades or something. The M203 (typically firing a standard frag) is a single shot, breach loaded weapon, and it adds considerable mass to the rifle. Having an additional magazine tube besides the launcher would be, IMO, excessively bulky.
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CRMcNeill
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PostPosted: Tue Aug 01, 2017 2:31 pm    Post subject: Reply with quote

I got the idea of a pump-action grenade launcher from the Aliens movie, where the pulse rifles were fitted with a 30mm pump-action launcher, where the grenades could either be fired by the launcher or thrown by hand. And yes, 30mm is a lot bigger than most shotgun shells, but I don't imagine it would be too difficult to scale up pump-action tech to match.

Plus, Star Wars has a track record for reduced sizing in explosives; proton torpedoes and concussion missiles are tiny compared to current tech.

As far as using Cover & Concealment rules to represent the advantages of ballistic shooting, I'm open to suggestions. Maybe increased Difficulty to hit, but with the ability to negate Full Cover, so long as that cover is only in one direction (I.e. No overhead cover).
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garhkal
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PostPosted: Tue Aug 01, 2017 3:01 pm    Post subject: Reply with quote

I can agree with that.. Make it that if you manage to hit at +5 over, you negate cover up to 25%. +10 to hit, negates cover up to 50%. +15 negates cover up to 75%, and +20 or more negates any cover..
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MrNexx
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PostPosted: Tue Aug 01, 2017 3:02 pm    Post subject: Reply with quote

I might go with a difficulty to hit a point or "square", depending on range and concealment, with modifiers for maximum altitude.

So, let's say I've got a grenade launcher, and want to drop a grenade behind an improvised set of cover about 15m away. If I'm in an open hangar, this is pretty easy; I can loft the grenade pretty high, and drop it easily behind that stack of TIE Fighter panels they're hiding behind. If we're in a standard 3m tall corridor, though, I'm going to find this harder, since I can't get the same loft to drop the grenade right where I want.
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Naaman
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PostPosted: Tue Aug 01, 2017 4:11 pm    Post subject: Reply with quote

A stand-alone pump action grenade launcher males sense to me. But an under-barrel attachment pushes my imagination beyond suspension of disbelief. That's all I was trying to say on that one.

As for negating cover, an HEDP grenade would punch right through the cover and blow up on the other side. The air burst mentioned by dredwulf also has application.

What is tieing me up is the concept of shooting (as opposed to throwing) a grenade over cover. Because of the fact that cover can be however tall and however wide, etc, it adds complexity to the situation that I'm not sure the mechanics of the game can easily support.

For example, firing over cover that is 30m tall is much different at 10m away than at 300m away or 1000m away. Also, the distance between the shooter and the cover affects the angle of the shot, but so does the distance between the shooter and the target. If the target is behind cover, the shooter doesnt even know what distance he needs to account for, so it may be easy enough to clear the cover, but then, you're stuck with whatever arch that angle of fire produces, and the point of impact is more or less predetermined regardless of whether the intended target is there or not.

If the shooter knows the precise location of the target, I would allow some kind of roll (perhaps missile weapons skill or scholar:ballistics) to determine whether the target can be hit at that distance given the cover being used.

Other than that, if the cover is low enough that the distance to the target already dictates that the natural arch of flight will clear the cover, then I'd use the normal (house) rule to hit, and provide the target a dodge bonus if he is concealed. If he is not concealed (for example, his head is popping up from behind cover), then no bonus at all.
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Bren
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PostPosted: Tue Aug 01, 2017 5:56 pm    Post subject: Reply with quote

I'd just go with letting the grenade launcher make a called shot to get around/over the cover with the difficulty set by the GM based on the circumstance. Success negates some or all of the cover. Failure hits the cover (and bounces back or detonates depending on the type of fusing) or overshoots the target or something. I'm thinking it might be handy to have some sort of grenade scatter chart for the misses.
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