Sentry Bot (Fallout 4)

Sentry bots are a type of robot found in the Commonwealth and Nuka-World

Characteristics
Sentry bots have powerful melee attacks and a self-destruct function along with weaponry. A sentry bot's entire torso is capable of rotating independently of its legs, functioning akin to a turret and allowing it to move in one direction while shooting in a different direction.

Should a sentry bot engage the player character for too long, they will eventually enter a cooldown period, blasting steam out of their back and exposing their dual fusion cores. Hitting exposed fusion cores is the best way to cause damage to them. All legendary robotic enemies explode upon destruction, which means a legendary sentry bot will explode twice. Sentry bots drop at least two fusion cores when they are destroyed, along with other valuable electronic components.

Sentry bot
The basic version of the sentry bot, this type of sentry bot is the weakest of the sentry bots in Fallout 4 but it still a difficult combatant compared to other robots, mainly due to its high Hit Point pool, a high Perception on par with Assaultrons, above average Damage Resistance and Energy Resistance and high-powered armaments (either 2 5.56mm miniguns or one and a missile launcher).

Gunner sentry bot
These sentry bots are exactly like the original ones except the fact that they have been reprogrammed by Gunners and have a faded green tint, similar to a Mister Gutsy.

Siege breaker sentry bot
A rare, higher leveled stronger variant of the normal sentry bot. This type of sentry bot can deal lots of damage towards their enemies, have a higher Perception of 9, higher Damage Resistance and Energy Resistance, and 100 more Hit Points.

Gunner siege breaker sentry bot
The same type as the siege breaker sentry bot, only it is only under Gunner command. They will attack anything that isn't a part of the Gunners.

Annihilator sentry bot
A tougher and stronger variant of the sentry bot, having 150 more Hit Points (totaling 1000), higher Damage Resistance and Energy Resistance and maxed-out Perception, making it difficult to sneak up on. The annihilator is also armed with dual high-arcing mortar launchers, which at long range can hit targets even if they are behind cover. At closer range, the annihilator may switch to its standard sentry weapons.

Gunner annihilator sentry bot
A Gunner variant of the annihilator sentry bot. These can be very powerful along with their gunner comrades and are often armed with missile launchers.

Annihilator sentry bot Mk II
Similar to the standard Annihilator Mk I but the mortars fire a timed explosive clump (grenades appear to be glued together) rather than a concussion shell increasing its usefulness in indoor areas and urban environments, this as well as having a further increased Hit Points results it being a formidable opponent.

Gunner annihilator sentry bot Mk II
A Gunner variant of the annihilator sentry bot Mk II, identical to its counterpart except for it programming to kill everything but Gunners.

Combat sentry prototype MkIV
An inactive combat sentry prototype MKIV can be found at the robotics disposal ground. Inside the shed near the entrance to the facility, there is a terminal that has a holotape loaded. Initiating the holotape on the terminal activates the sentry bot outside, after which it immediately starts to patrol the area. By ejecting the holotape from the terminal and using it in the player character's Pip-Boy, the Sole Survivor can command the sentry bot to go to different locations in the Commonwealth to clear of enemies, after which it will return to the junkyard. However, these locations are limited to nearby military sites. Once activated, the Sole Survivor can interact with it via the Robotics Expert perk to further the commands for it.

Sentry bot lament
The sentry bot lament has been modified by the Rust Devils. They may be found accompanying Rust Devil patrols throughout the Commonwealth.

Sentry bot reaper
A powerful variant of the sentry bot, usually armed with a Gatling laser and a minigun. Due to its heavy armor covering most of its body, it has a high Ballistic damage resistance.

Space sentry
The space sentry (or Model X9000 according to maintenance terminal in the RobCo Battlezone) was a prototype of the sentry bot that was in development before the Great War. RobCo built several prototypes to showcase at the Nuka-Cola Corporation's Nuka-World amusement park in the Galactic Zone, primarily in the RobCo Battlezone. It features a shiny white paint scheme with gold accent colors, redesigned armor, leg mounts and wheels, a plastic dome around the head area resembling a helmet as well as new "space laser" weaponry (standard lasers renamed) and Nuka-launchers.

Space sentry breaker
A higher leveled stronger variant of the normal space sentry bot, with higher Perception, Damage Resistance and Energy Resistance, and 100 more Hit Points.

Space sentry annihilator
An even further improved version, the space sentry annihilator wields a powerful Gatling laser and is able to launch missiles.

Space sentry obliterator
An extremely powerful version of the sentry bot, found in the RobCo Battlezone in the Galactic Zone. Only one exists in the Commonwealth.

Locations

 * Northwest of Murkwater construction site and south of Suffolk County Charter School is what appears to be a partially submerged power station, with only the pylon towers above water. If the player character opens a door in the central pylon tower they will see a cinder block wall, with both a graffiti message that reads "YOU LOOK NICE TODAY!" and the same red skull decal used in Halloween decorations just beneath it. A sentry bot will spawn on the opposite side of the tiny building and start attacking the player character. Like other sentry bots, this sentry bot is level-dependent, e.g. at player character level 63 it is an Annihilator Mark II.
 * Directly northeast of Murkwater construction site is a memorial to fallen soldiers, guarded by an initially inactive sentry bot.
 * A sentry bot will attack the Sole Survivor after they exit the National Guard armory. When the cell resets, the sentry bot can be found patrolling the hill around the armory.
 * West of Somerville Place and east of Vault 95 is a sentry bot in a cage, guarding a locked storeroom on a slight hill. Picking the lock and entering the storeroom, or attacking this sentry bot directly, will activate and release it.
 * One is guarding an abandoned caravan on top of the small hill west of Medford Memorial Hospital.
 * A sentry bot will attack you at the top of the 35 Court building.
 * An inactive sentry bot is present in Hester's Consumer Robotics, which will immediately explode if attacked.
 * There's a chance of a sentry bot spawning near the collapsed highway between Easy City Downs and East Boston police station.
 * Two sentry bots attack the player character after obtaining the Beryllium agitator in the Mass Fusion building.
 * Two can be found by and on the bridge southeast of Lynn Pier Parking, there are also an Assaultron and Mister Gutsy on a barge after passing the bridge.
 * North of the South Boston military checkpoint, at an unmarked Red Rocket.
 * On the broken highway just west of Flight 1981 at a Gunner outpost.
 * West of Fairline Hill Estates and northeast of Egret Tours Marina. It is locked inside a maglock-locked building and will attack along with two Protectrons if the terminal controlling the door is hacked.
 * Northwest of Coastal cottage is a Gunner outpost on a freeway that's guarded by a sentry bot and Assaultron.
 * One patrols the road west of Fort Hagen that leads up to the Fort Hagen satellite array.
 * One roaming the road southwest from ArcJet Systems/southeast from Federal ration stockpile.
 * An inactive sentry bot can be found in the Old Robotics section of the Institute. It can be activated with the robotics terminal. It will fight the synths that are on the assembly floor, but will also be hostile to the player character.
 * A non-hostile sentry bot is guarding the outside of Cabot House.
 * At the robotics disposal ground there is a sentry bot that is deactivated. It can be activated by using the combat sentry proto MK IV holotape that is in a small building nearby.
 * One is found in the Nuka-World Junkyard, under the ledge of garbage that the large red alien saucer is sitting on.
 * A space sentry can be found in the RobCo Battlezone, in the arena after the other smaller robots are defeated.
 * Behind a limestone wall in Vault 88 in the area before the East sector.

Named sentry bots

 * Ahab (hostile) - encountered inside the Fort Hagen satellite array.
 * Ironsides (non-hostile) - leader/captain of the USS Constitution.
 * Gus (non-hostile) - in a special encounter, sentry bot that roams with the small merchant girl, Kat.
 * Porter (non-hostile, destroyed) - part of Jackson's caravan.
 * Sarge (hostile) - encountered inside the armory of The Castle in the quest Old Guns.
 * Startender (hostile/non-hostile) - encountered in the Starlight Interstellar Theater.
 * Combat sentry prototype Mk. IV (non-hostile) - encountered at the Robotics disposal ground.

Automatron
With Automatron installed, the Sole Survivor can build their own sentry bots at any robot workbench. They can then be ordered to follow the Survivor like any other companion.

Appearances
Sentry bots appear in Fallout 4 and its add-ons Automatron and Nuka-World.

Bugs
At the robotics disposal ground, the prototype sentry bot MKIV does not move once powered on. There are a number of fixes:
 * Fast travel elsewhere and sleep.
 * Using the Robotics Expert perk to disable and then reactivate the sentry bot.
 * Enter the console and click on the sentry bot, type, then.
 * If activated and it still won't move, deactivate either by hacking or the holotape (may say data corrupted), hit or shoot it once, then activate it.