(Only publishing because I keep having to build it and post it on other sites)
Required Gear: -Red Fang legendary class mod
A lot of people say that Gamma Burst builds are too gear dependent, but this build isn't all that dependent on anything other than the class mod I just listed. It allows your pet to taunt all enemies while Gamma Burst is active. It's only required for two reasons. 1) Proccing enemy aggro while gamma burst is active helps an insane amount when mobbing and 2) Since enemies are targeting your pet, you'll get the 30% damage boost from Hidden Machine.
You can use whatever weapon set up you want. The rad set up (Pestilence pistol, Red Suit shield, and elemental projector) can be used with this build with little difficulty, but the build isn't dependent on that particular loadout. A lot of people also say that it's gear dependent since you have to get all of your weapons in an anointment that gives 65% radiation damage while gamma burst is active. While those anointments may help, you will get enough of a damage boost while Gamma Burst is active to not need it.
As far as anointments go, look for anointments that boost weapon damage on action skill end (ase). That will give you a nice damage boost to make up for coming out of Gamma Burst, and will allow you to get the cooldown a lot quicker when combined with Eager to Impress.
Augments: You can switch out Endurance for Burst Aid if you want. Just be aware that there is currently a bug that plagues Burst Aid that makes it so it doesn't always heal you.
Now, let's get to the build. :)