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Borderlands 4 Build

Gamma Ray Burst - BEST GUN HARLOWE BUILD

presentationHarlowe
End Game
Leveling
presentationFlux Generator
Creator
Featured
Updated on Nov 23, 2025
Nov 23, 2025

Build Overview

THE ULTIMATE GREEN TREE BUILD!

SaveFile

This is the true Endgame Green Tree Gun setup for Harlowe

We are making use of Gamma Ray Burst to convert our shield capacity (which can go up to 120K!) into pure damage.

We are also taking advantage of the fact that some Gun's Alt-Fire like Kill Drone, Taser, Space Laser,... can retain the Amped Gamma Ray Burst Damage.

While you can't use just any gun in this build, it compensates for the amount of damage you will do with the guns that you are actually using (The Space Laser Oscar Mike can get up to 10M DPS!)

This takes huge inspration from Ratore's Dronemancer Vex

Strengths And Weaknesses

  • Damage
  • Survivability
  • One shot everything
  • Did I mention damage?
  • Gear specific

Skill Tree

Points Spent 0 / 49
LMB Allocate
RMB Unallocate
Flux Generator
5/5
2/5
5/5
3/3
5/5
5/5
4/5
5/5
5/5
5/5
  • Mains Hum and PPE are multipliers to our damage since we are using Gamma Ray Burst.


  • Decoherence and Latent Charge are great "bonus elements" that also take into account the damage of Gamma Ray Burst.


  • Nuclear Winter gives us a bonus element that can Entanglement, proc Distribution Function and Confirmative Reality.


  • Group Study gives us a ton of formula and an easy way to proc Gamma Ray Burst


  • Distribution Function allow us to get our shield back up faster and get more Gamma Ray Burst value through Nuclear Winter, Make Extraordinary support Nuclear Winter DPS thus also help Distribution Function greatly.


  • If you are struggling at irradiating enemies, swap Neutron Decay for Creative Overflow

Equipment

Weapons
Repkit & Ordnance
Utilities

GUNS:

  • Oscar Mike's Space Laser Alt-Fire - Great for bossing, each damage tick get Gamma Ray Burst, peak damage for non bugged gun in this build.


  • Order AR's Kill Drone Alt-Fire - Best option for mobbing, decent at bossing (inconsistent against flying bosses), both the Drone shot and explosion get Gamma Ray Burst.


  • Vladof SMG's Taser Alt-Fire - Solid option overall, each tick of damage get Gamma Ray Burst but stay in Shock.


  • Maliwan Shotgun's Energy Disc Alt-Fire and Kickballer with a Jakob Part go crazy in this build (up to ~100M DPS) but they're uninteneded so I wouldn't rely on this long term.


  • Death Sphere, Ordnite Spike, Attack Drone are all great option but they are one tier lower than the thing mentioned above.


ORDNANCES:

  • Firepot - is the best QOL ordnance option here, can proc Nuclear Winter which mean Distribution Function, can stack Riddle You This and Confirmative Reality. Can also do good damage on its own


  • Slippy is great against Vile enemies


  • Maliwan Heavy Weapon with a Mirv part is great with the splat 3/3 high caliber interaction, each mirv orbs get Gamma Ray Burst, best damage ordnance option.


  • Streamer - Each damage tick from beam gets Gamma Ray Burst, great damage ordnance option.

COMS:

  • Get the Radiologist COM with the as much point into Gamma Ray Burst as possible (5), this would allow 10/5 Gamma Ray Burst to drain 100% of our shield giving higher dps and better ammo consumption

SHIELDS:

  • Just get the shield with the highest capacity in your inventory, it is not worth it going for amp part on this build (amp does't not apply to Gamma Ray Burst)
  • If you want to target farm for a high capacity shield I'd recommend Cindershelly (Drop from Backhive)

ENHANCEMENT:

Very much depend on your gun

  • Hero of Bullet is great with Taser for example
  • It's better to focus more on the passives like Gun Damage, Gun Type Damage, Gun Splash, Gun Equip Speed.

REPKIT:

  • Use any repkit that gives 200% Amp
  • For guns like taser (that have low base damage), it's better to go for survivablity repkit or soup repkit

Firmware

Repkit & Ordnance
Repkit FirmwareDeadeye
Ordnance FirmwareDeadeye
Utilities
Class Mod FirmwareDeadeye
Shield FirmwareBaker
Enhancement FirmwareEmpty

The listed Firmwares are the must have for this build:

3/3 Deadeye now work with Excited State to give us a lot of soup for both the main shot and Gamma Ray Burst

1/3 Baker give us more shield capacity for Gamma Ray Burst

Oscar Mike, Bullets to Spare, God Killer are great filler option

Specialization

Specialization 1Riddle You This
Specialization 2I Am A Gun
Specialization 3Bullet Train
Specialization 4The Best Defense

Riddle You This - a lot of gun soup

I Am A Gun - is actually skill damage, help to support Nuclear Winter

Bullet Train - good gun QOL

The Best Defense - decent soup could be replaced by Groundbreaker for better bossing


Max out the tree that gives you Max Health and Shield first

Gameplay

BOSSING:

Activate your action skill

Retrigger it

Make sure you are using the correct mode of firing

Profit.

MOBBING:

Basically the same as bossing but now you would want a gun like the Katagawa's Revenge to get your action skill back fast with Confirmative Reality

You would want to get multiple copies of the some alt fire guns ready in all 4 weapon slots (especially when using drone) because we have no way to spam it on Harlowe

Changelog

23rd Nov 2025 - Added the Rooker, Slippy, changed the firmware list to include 3/3 Deadeye and some minimal skill tree change and updated the save file

Video Guide

Table of Contents

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