Fresh n00b here; might as well jump in and ask some questions. So far my search-fu has failed me.

I've got a player who's interested in building a drone that works very similarly to the ED-209 from the old robocop movies, minus the incompetent malfunctions. What this really boils down to, however, is a set of twin light machineguns on one large drone.

This is where the debate comes in: how would a drone target and attack with two weapons simultaneously? Initially I had thought of using the 2-weapon fighting rules that have you split the die-pool on attack, but something doesn't quite sit right with me there. A drone should be much more coordinated than that.

One idea we came up with was to set up the limbs as autonomous drones in their own right, each following "orders" from the main drone on what to shoot at, allowing each weapon-limb/mount to make its own attack roll.

I'd still like it if there were simpler rules for setting up linked-guns for drones and vehicles, and I've so far been unable to find any.

That leads me to a secondary questions about drones though: Why are almost all of them capped at a Body rating of 4?

Anyway, that's all I got for now.

You could have a Pilot/Sprite fire one, while the rigger/Technomancer/Person fires another, or even have one pilot per weapon. Essentially you can have one "operator" per mounted weapon. So the vehicle could have several mounted weapons, and one operator for each, and they could all fire as they have available actions.

It may help to consider the drone a vehicle, and the drone operator is the pilot, and the pilot will need to split actions between the operation of the vehicle and firing weapon. If you want both to happen at the same time, then you need an operator for each.

If you want a single operator for multiple weapons, then you could go use the two weapon rules as you've indicated.

I'm too lazy to look, but I remember seeing rules for putting commlinks in weapons in the Aresnal book. So you could jam a commlink into each weapon, smartlink it, and then jam an agent into the commlink. Then you just need to build one of those tracked hunter-killers from the terminator cut scenes.

SR4, 239, "Arm/Disarm a Weapon System (Free)
A rigger may order a single drone to arm or disarm one of
its weapon systems. A drone may have only one weapon system
armed at any one time. Switching weapon systems, however,
only requires one Free Action."

Thats basically what does it in, you can't get multiple weapons active on a drone at once.

What if it's technically multiple drones?

I know this looks like extreme rigger min-maxing, and I can see a world of potential abuse opening up here, so I'm kind of trying to get a feel for the ramifications.

I don't see it as being all that different than having multiple drones all following the same command; page 238 in the core book indicates you can have multiple drones all linked as a single device, meaning they basically follow the same command.

It would be expensive as hell running what would amount to three independent drones all on one platform, but I don't see anything that would technically prohibit it. I had thought about imposing a 1-die "coordination" penalty for having independent drones all slapped together, since it would be a little tricky for them to coordinate their movements to work in concert.

I'd give the weapon "drones" the -3 for firing from a vehicle for shooting while not controlling the movement, same as a character.

strictly speaking, vehicle mounted weapons can receive accessories, including those which use the 'under' mount. among those accessories is the smart firing platform. that's how i would handle it, personally.

But that brings into question if the weapon is sitting on the tripod, and able to be pivoted, or if its mounted on the vehicle with a tripod hanging off the bottom.

My vote goes to the latter, which means that the tripod will try to aim it, and sit there spinning uselessly. Unless of course you don't mount it on the vehicle as a vehicle weapon, which goes into house rule territory.

no special rules are given for whether or not firearm accessories function normally when mounted in a vehicle. the default rule is that they do work, with no indication given that this changes when you mount them in a vehicle, therefore by default they do work.

your personal ruling as a GM can change that, but then again your personal ruling as a GM can also change whether or not they work at all in the first place, whether vehicle mounted or not.

Actually, if it isn't mounted in a manual control mount, then it can only be fired by the person controlling the vehicle.

Going to completely different direction than the other posters, you could always just pick up a HV-HMG and assume it consists of two smaller MGs. The only drawback to that method is that you can't actually split fire between targets, but I'm not sure ED could, either.

Well, if they're within a couple meters of each other you can hit both with the same full auto attack.

I had thought that was the case, but didn't want to make a guess without my books in front of me. We almost never use the FA rules for anything.