So, when I played a long-ago homebrew of 40K, one of the things we ran into were automated sentry turrets, sort of like the ones in the uncut version of Aliens. Basically, every time we visited a new world, the cultists had already liberated the armory, and seized several key military structures, or we were breaching into hidden bases, but we were Space Marines, so it wasn't too bad. Anyway, one of the things both setups liked to do was to have long hallways, filled with 90* turns, and automated turrets at the far end (sort of envision a heavy stubber, on a turret, with an attached servo-skull, or some such). If we came around the corner, boom!, we got shot at. Combine the dark conditions we often encountered, and the alcove the weapon was often situated in, casting shadows over it, and providing some cover, and it made for a great deterrent, had we been regular guys, and not Astartes (they more slowed us down then hurt us, but made for great defenses when we had to hold the base against other cultists, after our NPC tech-priest refurbished them, and got control of the base core-cogitator). I could easily see a group of Explorers poking around an old base, left derilect, only to discover that automated defenses are still functional, protecting whatever treasure brought the Explorers there, in the first place.

So anyway, is there such a thing in the books, already? I wouldn't mind having to write it up, but I would rather not, if they already have. Also, I'm not entirely sure what sort of Ballistic Skill to give the machine spirit running the gun. Tech-advanced Tau drones are BS 20 (sort of sad for the shooty Tau), while Erioch servitors are BS 35, and spirit-fired Land Raiders are BS 50. While I certainly expect that the LR's is a high outlier (special machine spirits, crafted for that express use), it seems that the Imperium, at least, has the ability to make some smart auto-guns. Where between 20 and 40 seems a good spot to set it? Could it have Talents, and Skills, like a Servitor would? I figure it will have visual sensors, and night-vision, maybe covered by an integrated servo-skull, so maybe it could have other stuff, sort of a servitor in a different shape. As for ammo, I plan to have it hopper-fed, from a cavity that works like a backpack ammo pack, holding say four clips of ammo, situated below the floor, or being fed from a distant generator (in structures, anyway). In the right scenarios, having it take a full round to aim (as a full-auto weapon, like a heavy bolter, takes a full attack, one easily could aim the round before, while the party is slowly walking up the path), it could do some serious damage to any roving bands of players. It could also dash their hopes of sneaking in, as the sound of a heavy bolter would echo through whole regions of said base.

So, thoughts? Suggestions? Are these already in a book, somewhere? Thanks much.

Somewhere on the Lexicanum is a page detailing what all is in a Space Marine Fortress. They have something like 600 Machine Spirit controlled defense turrets or some such. So yeah, 99% sure it exists.

Yep the Metalican I, II, III and IV pattern sentry gun, aka the Tarantula. You could stick twin-linked heavy bolters or las cannon in them, they had a BS of 2 in the game, (which roughly = 20-29 in the RPG) on a fixed 90 degree arc of fire. The Imp Guard, Arbites and Astartes use them, they're also completely automated with a little logic engine in them so they dont need someone to tell them what to do.

Fairly cheap, sh*tty and mostly miss what they where aiming at otherwise

Okay, I'll be a smidge more specific. Are there rules/stats printed in any of the FFG books? I figure Only War might do them, if no other book has, but I don't know if they are printed, already. Otherwise, I think I could enjoy using the various printed servo-skulls, for senses, some skills, etc, and have a turret-mounted heavy weapon attached to it. Ballistic Skill 25-30 would be the likely setting. Picking a cheesy weapon, like a heavy bolter, or anything that fires full auto, should get the +20 BS, so it actually MIGHT hit, more often than not, and 240 rounds could last quite a while, even at full auto.

unless it's in one of the adventures: no

I think that you want the "Defence Turret" in the DH Book of Judgement (in the adventure at the back); equipped with two lasguns, although the illustration looks more like twin lascannons, part of the automated defences of a Tech-Priest's lab.

DW

Drop Pods, page 182 of Into The Storm, have automated storm bolters mounted on them.

Servo skull, laspistol, red dot laser sight. BS 25 when firing single shots.

For something heavier, just take the battle servitor and chop its legs off. One heavy weapon, four clips of ammo in an armoured hopper, no melee capability.

Personally, I have no problem in taking existing statlines and redressing them if I need something different. Know what I'd do if I needed a Gauss Turret? Chop the legs off a Necron Warrior and increase it's weapon damage and penetration by one each. Simple!