The premade weapons in the books aren't really made for drones. They don't need recoil comp, they can't (to my knowledge) use smartlinks or laser sights, and they don't really care about internal magazine size. How would you go about building guns for drones? I'm especially interested in LMG's (for medium drones), HMG's (for heavy drones), and alternative options like a ferret swarm armed with tasers, as well as extras like underbarrel grenade launchers. Fudging is fine within reason; the Arsenal rules for building guns don't really take vehicle weaponry into account, and I see no reason why electronic firing and trigger removal, for example, shouldn't be considered standard (no cost, nuyen or capacity). Modifying existing weapons is good too. Go nuts!
I'll start with a grenade launcher I built a while back. I used the ammo skip system rules in a way not explicitly allowed for (they put rules in for modding it on, but not for including it in the design), but I think the way I used it makes a lot of sense. I give you the "Skipper" underbarrel grenade launcher.
"Skipper" Underbarrel Grenade Launcher (Based on Ares Antioch-2):
The Skipper, due to its unique cylinder design and ammo-skip system,
allows Shadowrunners with smartlinks to avoid unnecessary fumbling
in order to find the right grenade for a given situation. Comes with
an integral smartlink and optional airburst link (+500). The Skipper
is specifically designed as an underbarrel smartweapon; treat it as
having the electronic firing and trigger removal mods. It doesn't
have a handle, so you'd have to retrofit it if you wanted to use it
alone. Note that the ammo skip system in the Skipper works like a revolver:
it doesn't eject, it cycles.
Damage as grenade
SS
1 RC
8 (cy)
8F
+600 (base)
+250 (ammo skip system)
=850 (basic model)
+500 (optional airburst link)
=1350 (with airburst link)
I'd personally fudge the cost down a bit (probably just to 800/1300, but possibly lower), as it was designed this way and the 250 ammo skip system cost is straight from the modding section.