Sentry Buster

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Sentry Buster
Sentry Buster
Basic Information
Health: 2500
Speed: 187%
Essentially a bomb on legs, the Sentry Buster will detect any sentry that’s dealing sustained damage to the Robot Horde, then initiate its deviously complicated protocol: run at the offending sentry and explode.
Mann vs. Machine publicity blurb

The Sentry Buster is a specialized robot that appears in Mann vs. Machine when a Sentry Gun has dealt significant damage to the robot horde. It appears as a large pair of legs similar to a Demoman Robot, but with a large naval mine for a torso.

Once a defending Sentry Gun has reached a certain amount of kills or damage (see Spawning requirements), a Sentry Buster is dispatched; they do not appear under any other circumstances. Once deployed, the Sentry Buster makes a beeline for the Sentry Gun that triggered its appearance. Additionally, a voice response from the Administrator, the Engineer who built the targeted Sentry Gun, and, in some cases, from friendly Heavies, Soldiers, and Medics is played to alert the team of the sentry buster's appearance. Upon reaching its target, it crouches and begins beeping. About 4 seconds later, it detonates in a massive explosion guaranteed to level the offending Sentry and just about anything else within approximately a three-Teleporter radius, including other non-giant robots around it. If giant robots are in the Sentry Buster's explosion as it detonates, the giant only takes 600 damage. If another Sentry Buster is caught in the explosion it also begins its own detonation, even if it is still in spawn or ÜberCharged by a Medic bot. The splash of the explosion will pass through the Medic's Projectile Shield, if you are still in range.

While inattentive Engineers are sure to lose at least their Sentry to a Sentry Buster, aware ones with a competent team can deal with it without too much trouble. Sentry Busters can simply be killed before they reach their target, which causes them to wind up and explode prematurely. Hauling the Sentry after Sentry Busters get close to the Engineer's sentry is recommended, as Sentry Busters cannot move once they begin counting down, but that does not protect any other buildings or teammates that may be nearby. An Engineer picking up his Sentry and carrying it around the map is not recommended, as it stops the Engineer and his Sentry from attacking the rest of the horde and attending to his other buildings. Knockback can keep a Sentry Buster at bay long enough to destroy it, but once they begin the detonation process, they are immune to it (excluding compression blast). However, regardless of how a team defeats a Sentry Buster, the robot horde continues to send them out after a mission-specific delay time until the target Sentry is destroyed or the wave is completed. The Rescue Ranger allows an Engineer to pick up his Sentry Gun from a distance, assuming that he has at least 100 Metal. This allows him to safely wait until the Sentry Buster starts detonating, then quickly withdraw his Sentry Gun before it explodes.

Sentry Busters spawn against and target Mini-Sentry Guns, but they ignore Disposable Sentry Guns, even if it is doing more work than the primary one. If a Sentry is destroyed before the Sentry Buster gets there, it continues running to where the Sentry used to be and then detonates. If a Sentry dies high enough in the air (in the case of an Engineer dying midair while hauling one) before the Sentry Buster can reach the Sentry Gun, it runs around the area directly below, often giving up and detonating after a few seconds. Rarely, they may become stuck and not detonate for a few minutes, or if the team sufficiently damages it. These Sentry Busters do not prevent new Busters from spawning, and a new one spawns after the cool-down period, as long as the Engineer rebuilds the Sentry and it is not destroyed by other robots. A Sentry Buster self detonates if it cannot find a path to a Sentry Gun.

Destroyed Sentry Busters, whether by themselves or by the players, leave no credits. A large cloud of dark grey smoke lasting a few seconds remains after detonation, blocking the view of players within the range of the smoke.

Spawning requirements

The Sentry Buster only spawns when a Sentry Gun reaches a specific kill or damage threshold. This threshold is dynamic depending on the amount of non-disposable Sentry Guns on the map, decreasing with every additional Sentry Gun, up to a maximum of six Sentry Guns. These values are the same for every Valve-made mission, however, custom missions can set custom thresholds with the attributes AddSentryBusterWhenDamageDealtExceeds and AddSentryBusterWhenKillCountExceeds. Each Sentry must hit one of the thresholds for a Sentry Buster to spawn for that Sentry Gun. Sentry Busters spawn in waves depending on their cool-down times, which is mission-specific (in some cases, such as Bavarian Botbash, the cool-down times are also wave-specific). The first wave of Sentry Busters also has a per-mission (in some cases, per-wave) delay, and cannot spawn until a certain amount of seconds has passed since the wave began. Only one Sentry Buster spawns per Sentry per spawn wave. Kills and damage dealt is only reset when a Sentry is destroyed by the robots, or if the wave ends. If an Engineer destroys their Sentry one kill before a Sentry Buster would have spawned, then one spawns when their next Sentry gets a single kill, provided the robots do not destroy it while it is building.

Sentry Guns Kills Damage
1 15 3000
2 13 2700
3 12 2400
4 10 2100
5 9 1800
6+ 7 1500

Note: Giant kills count as 5 kills in regards to these kill thresholds.

Related achievements

Mvm navicon.png Mann vs. Machievements

Kill 5 robots in a single explosion from detonating a sentry buster.

Real Steal
Real Steal
As an Engineer, escape with your sentry as a sentry buster is about to detonate.
Ctrl + Assault + Delete
Ctrl + Assault + Delete
Destroy a sentry buster before it reaches its target.

Update history

August 15, 2012 Patch (Mann vs. Machine Update)
  • The Sentry Buster was added to the game.

August 17, 2012 Patch

  • Fixed Sentry Busters picking disposable buildings as valid targets.
  • Fixed an instance of the Sentry Buster sound looping endlessly.

September 16, 2013 Patch

  • [Undocumented] Sentry Busters now destroy robots when they explode.

September 18, 2013 Patch

  • Notes missed from Monday's update:
    • Updated Sentry Busters in Mann vs. Machine mode to damage teammates when they explode.

January 9, 2015 Patch

  • Fixed using the Holiday Punch to tickle Mann vs. Machine enemy bots.

July 14, 2016 Patch #1

  • Fixed sentry buster sounds not being cleaned up properly after detonating.


  • Only the legs are tinted yellow when soaked in Jarate, due to the material proxy required being missing from the material for the pressure mine segment of the model (demo_buster.vmt).
  • In the Halloween mission Caliginous Caper, Sentry Busters spawn with Demoman upper arms levitating at their sides and Spine-Chilling Skulls on their invisible heads.
  • Sometimes, when a Sentry Buster is killed, it simply vanishes instead of crouching and exploding. When this happens, the kill feed shows that the player killed the Sentry Buster with their weapon.
    • This can happen when for example, the Sentry Buster has 3 health and the attacker deals 2.5-2.99 damage to the Sentry Buster.
  • If the defenders lose the round, and the Sentry Buster is still alive, it does not detonate near Sentry Guns, but attacks enemies or enemy buildings as if it was a robot using melee instead of a Sentry Buster, and continues to do so until the round resets or the Sentry Gun dies.
  • Occasionally in Mannhattan, if the Sentry Buster is active when the robots capture one of the gates, it rushes over toward the capture point and stays there, disregarding the Sentry entirely until the robots become active again.
    • In this state, it attacks enemy buildings or enemies near it as if it was a robot using melee instead of a Sentry Buster. This is because of how giants behave in the map.
  • Pyros that airblast the Sentry Buster into mid-air as it detonates cause it to use the animation for idling, thus resulting in the Sentry Buster exploding while walking around or idling.
  • When a Sentry Buster is shot by something explosive, it uses the voice lines for a Demoman Robot exploding his Ullapool Caber.
  • If a Sentry Buster is shot while it is in the robot's spawning area, no ÜberCharge texture shows up.
  • Occasionally, it is possible to see the Sentry Buster's invisible Ullapool Caber floating in the air. This happens due to how Mann vs. Machine works; Robots and Sentry Busters keep "spectating" human players internally until they are ready to spawn and, when a Sentry Buster spawns, the Ullapool Caber gets fixed in the air on the same position of the player they were "spectating" prior to respawning.
  • As Sentry Busters can damage robots, they can "defend" the bomb if they destroy a robot that is carrying the bomb.
  • Kills or damage made by a Sentry Gun harming its Engineer can contribute to spawning a Sentry Buster.


The hitscan hitboxes of a Sentry Buster.
  • The model of the Sentry Buster references the design of naval contact mines iconic to World War I and II naval warfare.
  • The Sentry Buster is considered to be a giant Demoman wielding the Ullapool Caber. As a result, it shares animations and hitboxes with the giant Demoman Robot (resulting in having invisible arm and head hitboxes) and appears to be holding the Ullapool Caber in first-person view to spectators, with any kills credited to it using the Ullapool Caber kill icon. As voice responses do not appear to be disabled for the Sentry Buster, it uses the giant Demoman robot's voice clips when speaking. Voice commands, such as the "Spy!" one, also refer to the Sentry Buster as a Demoman. Additionally, since it has a head hitbox, it can be headshot for critical damage.
  • Since Sentry Busters become immune to damage and explode when their health reaches 1, it functionally has 2499 health as opposed to 2500.
  • A Sentry Buster's detonation is linked to its taunt function. This resulted in a now-fixed bug where forcing it to taunt via the Holiday Punch would cause it to explode prematurely.


See also