Sentry bot ( Fallout 4 ) Sentry bots are a type of robot found in the Commonwealth in " Fallout 4 " . Characteristics . Specifications . The Commonwealth variants of the sentry bot are similar in overall appearance to the ones encountered in the Capital Wasteland and Mojave , but are even larger ( on par in height to a human wearing power armor and nearly twice as wide ) , appear to have a bulkier construction and are substantially more resilient . The typical weapons loadout of the sentry bot remains the same as seen in " Fallout : New Vegas " , with a missile launcher and minigun being the norm ( except these miniguns appear to be unique 3 barreled variants chambered for the 5 . 56mm round ) . However , alternate weaponry configurations such as dual miniguns can also be observed . Annihilator sentry bots may also possess dual back - mounted mortar launchers , further enhancing their offensive capabilities . On top of their already formidable ballistic and explosive weaponry , sentry bots now have powerful melee attacks and a self - destruct function with equivalent power to a mini nuke . Some variants appear to have four legs instead of three as seen in the previous versions . They seem more durable than previous iterations of the sentry bot in other games , however despite being extremely bulky their mobility if anything has actually improved ; they are capable of moving stunningly fast and traversing extremely rough terrain ( even scaling rocky outcrops with little difficulty that the Sole Survivor would struggle to jump up on ) . In addition ; 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 ( potentially against targets directly behind it ) . A similar variant to the Commonwealth sentry bots can be found in " Fallout : New Vegas " at the REPCONN headquarters museum . Newer versions in " Fallout 4 " appear to use Mecanum wheels that allow it to strafe right and left without having to turn . Gameplay attributes . Sentry bots are some of the rarest and the most difficult robots to defeat - fast , agile , heavily armed and resilient enough to absorb a direct hit from a mini nuke . After losing both main weapons they will initialize their self - destruct sequence and charge at the player character . Even with their ranged weaponry intact , sentry bots often charge into close combat to deliver powerful blows with their arms if one ventures too close , thus deterring attackers from any use of melee weapons . Since they explode on death with the force of a mini nuke , this tactic may prove even more dangerous to their opponent than their devastating long - range firepower . However , 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 . Players having the Penetrator perk need not wait for cooldown , and can use V . A . T . S . to target and destroy the fusion cores immediately , making this perk invaluable for fighting sentry bots . Also , unlike other robots it completely lacks a combat inhibitor , thus completely removing the possibility of using that to the player character ' s advantage . Should one encounter a legendary sentry bot of any kind , keep in mind that all legendary robotic enemies explode upon death . This explosion does not override the sentry bot ' s built - in self - destruct , which means a legendary sentry bot will explode twice . Both explosions are equivalent to a mini nuke in power and occur with a short delay of a few seconds . Sentry bots are a good but dangerous source of fusion core s , dropping at least two when they are destroyed , along with other valuable electronic components . Variants . 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 . The name implies that they were intended to break enemy fortifications . 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 and Damage Resistance and Energy Resistance results it being a formidable opponent . 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 is a sentry bot that has been modified by the Rust Devils to suit their needs . They may be found accompanying Rust Devil patrols throughout the Commonwealth . 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 re - named ) and Nuka - launchers . 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 . " 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 . Owing to their sheer power , constructing sentry bots requires huge amounts of rare crafting components on par with upgrading X - 01 power armor , high levels of the Armorer , Science ! and Blacksmith perks as well as at least one point in Gun Nut and Robotics Expert each , assuming one wishes to access all available customization options . A fully upgraded sentry bot boasts a very large health pool , heavy armor , decent speed , the most powerful long - range weaponry of any custom - built robot type in the game ( up to and including twin Fat Man mortars mounted on its back ) in addition to a very strong melee attack even without specific close combat weapons attached to its arms , extraordinarily high carry weight and is capable of clearing out entire hostile strongholds on its own , given the right circumstances . On top of which ; automatron sentry bots are capable of manning guard posts at settlements ( with the guard tower ' s staircase being just wide enough to accommodate them ) . This grants a settlement with a decent amount of open space for the sentry bot to maneuver a level of protection far out of proportion to its supposed defensive rating and can potentially provide further assistance to any settlers during a raid if it is fitted with a support system granting damage resistance or health regeneration to allies . As powerful as they are , the sentry bots ' performance as companions suffers from a couple of drawbacks : Behind the scenes . The sentry bot in Fallout 4 may be based on the T - 1 tank featured in " Terminator 3 " , as they both have dual miniguns , the ability to swivel around the waist , and are both designed for military use . However , a difference is that the T - 1 propulsion system consists of tank tracks rather than mecanum wheels .