This tower replaces its arm with a super strong bionic arm. The Bionic Boomer throws boomerangs twice as fast.
~ Official description in BTD5
Replaces arm with a strong bionic arm that can throw boomerangs extremely fast.
~ BTD6 description
Bionic Boomer is the third upgrade on the second path for the Boomerang Thrower that made its debut in Bloons TD 5. Although the description states it fires twice as fast, it actually shoots much faster. In BTD5, it actually fires around 3.5x as fast as a non-upgraded Boomerang Thrower, 4.9x faster than a non-upgraded Boomerang Thrower with the Glaive Thrower upgrade. In BTD6, it will shoot ~5x faster than a non-upgraded Boomerang Monkey, plus even more attack speed with Glaives. The upgrade makes the tower shoot a nearly constant stream of projectiles, shredding the Bloons away. Although this upgrade diminishes the need for the Boomerang Thrower's need to be placed near an elliptical curve, the tower will do much better if it's placed near one. This is because the boomerangs/glaives' movement will "follow" the curve, covering that entire curve and popping bloons more effectively. However, it's almost impossible that the boomerangs or glaives follow that elliptical curve because, like most of the towers, the tower has its Target Priority. With the fully-upgraded Boomerang Dojo, this tower is extremely powerful as it is reliable. In both BTD5 and BTD6 it costs $1360 (Easy), $1600 (Medium), $1730 (Hard), $1920 (Impoppable).
In BTD6, this upgrade returns, increasing the attack speed by ~5x, to 0.3 seconds per shot. It also does +1 extra damage to MOAB-class. It can be unlocked with 2500XP.
There are several differences between the Bionic Boomer in BTD5 and BTD6. One of the main differences is that the name is now renamed as Bionic Boomerang. The other main difference, which is in terms of appearance, is that the Boomerang Thrower still keeps its jumpsuit, but it's now a grey jumpsuit, just like the one that the Faster Rangs upgrade has. Also, purchasing Bionic Boomer will not necessarily give it Red Hot Rangs anymore, as they are now on separate paths.