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A Dossier on the Giant, Three-Legged Metal Elephant in the Room

Tags: #Valentine Detective Agency Article 
  • June 3, 2017

    Sentry Bots: Their Strengths, Weaknesses, and How to Fight Them


    Sentry bots are just one of many reworked enemies in Fallout 4, and man did that rework do wonders. Whereas sentry bots were just another robotic enemy in other games, they instead act as mini-bosses in Fallout 4, laying down the law and giving out a whipping to those who aren’t qualified to handle them. They are tough, especially so if your character is not outfitted to fight them. Fortunately, you can prepare for almost every sentry bot encounter in Fallout 4, and that is what I aim to do.

    At their core (that’s a pun, but more on that later), sentry bots are three or four-legged metal monstrosities, capable of high DPS through multiple methods, they are a test for a player’s ingenuity, awareness, and inventory. Their weaponry consists of, for the most basic models, either one or two 5.56 miniguns, a rocket launcher, and powerful fists. The higher level sentry bots will also come equipped with mortars. Sentry bots are thickly armored, have high energy resistance, and a large pool of hitpoints, making them a pain to chip away at. However, there are some ways to remedy this problem. First, the stats.

    Sentry bots’ main weapons both do high, high damage. While each bullet of the 5.56 miniguns ‘only’ does 5 base damage (per shot), but the fast firing rate means that those bullets can cut you down if you stay exposed for too long. The damage also scales, going up to 10 damage per shot eventually. The missile also does high damage, at 36 per shot, but keep in mind that missiles frequently cripple limbs, leaving you exposed to even more deadly fire. The sentry bot’s melee attack does incredibly high damage for low levels, at 30. However, pure numbers do nothing to help you visualize these robots’ ferocity. So let me use the following examples to clarify:

    A player character with 4 Endurance will have 100 hit points to begin the game. If they attempted to fight a base-level sentry bot, it could conceivably kill them in three melee hits + less than a full second of firing a single one of their miniguns. A level 5 character with 4 Endurance will have 118 health (if they haven’t taken perks to raise it), barely raising their survivability.

    While sentry bots do insanely high damage, they are no glass cannons themselves. Base health for a sentry bot is 750, making them able to resist even a direct shot from a mini nuke. This high health is further enhanced by their damage resistance, and this is where it just gets ridiculous. Base sentry bots have 125 DR. The way that DR relates to damage in Fallout 4 is weird, but 125 damage resistance comes out to roughly 65 percent damage reduction. That means that, if the player does 50 damage to the sentry bot, it will actually only take around 17-18 damage in the end.

    Sentry bots also have several abilities/mechanics in combat. If you can last long enough, the sentry bot will overheat and “cool down” for a few seconds, exposing fusion cores on their back. This is their weak point, and it is very easy to destroy a sentry bot if you can get to their backside. That is a big if, however. Another mechanic is their self-destruct. If the player cripples both of the sentry bot’s arms, rendering it unable to shoot, then it will charge the player and explode it’s fusion cores, resulting in a mini-nuke level explosion. While on the topic of explosions, it is also worthwhile to mention that, when a sentry bot dies, it will explode as well. This is also a mini-nuke level explosion. 

    Now that you have the information, you have probably already thought of some tactics to use against these behemoths. The tactic the developers intended the player to use is, basically: wait out the storm in a good position, then sprint around and VATS the hell out of the fusion cores. However, this doesn’t always work. Often, you will be too far away for the very quick cooldown timer to be of any help. Instead, consider getting the Penetrator perk (lvl 2 of the perk requires Perception 9, lvl 28). This will allow you to hit the fusion cores at any point during the encounter, making the hardest part just getting out of cover long enough to line them up.

    Another deadly tactic that will turn these things to putty is the use of Plasma grenades and mines. Each plasma grenade can take about 1/3 of a sentry bot’s health away, and multiple plasma mines can do the same thing. Plasma mines can in fact be more effective, because they don’t require you to expose yourself. The sentry bot AI’s aggression level is at the highest possible, meaning these things will chase you and sometimes even attempt to engage in melee combat. This makes it easy to line up a path of mines as you retreat, not even having to draw a weapon.

    Tactics that you will want to avoid are mostly obvious. Melee and shotgun playstyles leave you too exposed to the heavy fire and countering melee strikes. The best playstyle against a sentry bot would be an upgraded sniper rifle + Penetrator Level 2 + mines.


    So there you have it. The mechanics, stats, and tactics to crush down these fearsome foes. It won’t be easy, but it can be easier. If I missed anything, please tell me. Any playstyles that I missed, or typos? Please comment about them.


  • Member
    June 4, 2017

    I love fighting Sentry Bots. It's just so intense and made my first playthrough where I didn't know their locations super scary during those "OH shit" moments when I heard one powering up. Bethesda definitely used these in a way that made them very memorable.

    I appreciate the information on how to deal with them better. Penetrator perk? Never thought of that; genius! You mentioned their self destruction capabilites when they're disarmed, but I don't believe you mentioned the explosion they make after you fully kill them. It does do damage right? I feel like I remember fighting the one under the Castle (small coridoor) and dying after finally killing it because of it's on-death explosion. Other than that I believe you nailed every aspect of Sentry Bots, excellent job Probs!

  • Member
    June 4, 2017

    Legit never occured to me to use penetrator perk on the cores. awesome work. I agree, a small addendum regarding self-destruct explosion is needed. I've died so many freaking times that way. :/

  • June 4, 2017

    Had zero clue that Penetrator was a Sentry Bot hard counter. That makes it seem much much more appealing. Might roll me a...I don't know, robot-killing rifleman just to test that out. 

  • June 4, 2017

    Yeah the Penetrator perk is often ignored, just because it's so high on the perk chart and has a fairly high level requirement before it can be used effectively against sentry bots, but it REALLY works. 

    Thanks for the suggestion Madd and Motty, I'll put it in right now. 

  • August 16, 2017

    So I was finally able to see this in action, though I was able to do it at Penetrator level 1. Killed a Sentry Bot guarding full T51b. The assaultron was there too, but it's the Sentry Bot that matters.