For the BTD5 version of this upgrade, see Sentry Gun (BTD5).
Creates temporary sentry guns and deploys them nearby.
~ Official Bloons TD 6 description.

Sentry Gun is the first upgrade of path 1 for the Engineer Monkey in Bloons TD 6. It allows it to create sentry guns within its range every 10 seconds. Each sentry lasts for 25 seconds, meaning on average the Sentry Gun creates 2.5 sentries (in-game between 2 and 3). The creation of sentries is affected by attack speed buffs such as Jungle Drums Villages.

The Sentry Guns shoot nails every 0.95 seconds, and each nail can pop 2 bloons (3 with Oversize Nails) and they have a range of 45 (+4 with Larger Service Area). The nails are of the sharp damage type and cannot pop lead or frozen without special upgrades. Crosspathing with Oversize Nails changes the sentry damage type from sharp to shatter (sharp + frozen-popping).

It costs $425 on Easy, $500 on Medium, $540 on Hard, and $600 on Impoppable

Strategies[edit | edit source]

Summary[edit | edit source]

Sentry Gun is traditionally the main feature of the Engineer that gives him the edge at early-game, and it remains true in BTD6. In essence, the Sentry Gun upgrade provides the Engineer with an attack that allows him to deploy nearly statistically equivalent 0-0-1 Dart Monkeys nearby. These sentries give the Engineer with considerable early-game damage, especially while combined with the fair attack speed and pierce of the base Engineer himself.

Tips[edit | edit source]

  • Sentries spawned from the Engineer will automatically be set to whatever the Engineer's target priority is. They can also be manually changed to a specific target priority.
  • It's usually best to start crosspathing once further upgraded to Faster Engineering, as increasing the production speed further is far more effective than range or pierce crosspathing in most situations.

Version History (BTD6)[edit | edit source]

12.0 (compared to BTD5)

Nerf.png Pierce of Sentry Gun decreased (2 --> 1)

12.1
  • [Bug Fix] 110 Larger Service Area now increases Sentry deploy range.
  • [Bug Fix] Nerf.png Fixed a bug where Bloon Trap granted camo detection and lead poppage to sentries
15.0
  • Buff.png Standard Sentry pierce increased from 1 to 2
17.0
  • [Bug Fix] 1xx Sentry Gun sentries no longer gain camo detection when a save is loaded
  • [Bug Fix] 1xx Sentry Gun sentry placement will no longer ignore 'smart placement' if the Engineer cannot reach the track
20.0
  • Buff.png 110 Larger Service Area now applies 1/5th the range (+4) to any sentries produced
  • Buff.png 101 Oversize Nails allows sentries produced by this tower to pop frozen Bloons
  • Buff.png 101 Oversize Nails now increases sentry pierce by +1

Ninja Kiwi stated in the 20.0 Patch Notes that the reasoning behind these changes was "continuing our efforts to make crosspaths meaningful" and to "fit the style of each path more solidly".

Gallery[edit | edit source]

Trivia[edit | edit source]

  • Before the sentry pierce buff in Version 15.0, Sentries were the only non-hypersonic one-projectile towers to have only one pierce.
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