Thump-Thump is a unique Grenade Rifle that can be found inside the locked Nellis Array building located within the Nellis Air Force Base, the key to which can be obtained from Raquel.

Quick tips before I get into the guide:

• Exploding ants. The ants inside the Nellis Array building are different from the regular ants in that if you kill them with explosives, fire, or laser/plasma attacks, they will explode when they die. Be careful to not be within the blast radius.
  • This can be used to your advantage if you can hide around a corner quickly enough, as you can clear an entire room of ants if you explode one. Exercise extreme caution if you intend to use this strategy.
• Watch out for the artillery barrage. If you’ve never been to the Nellis Air Force Base, you’ll have to get past an artillery barrage to enter. Refer to this guide for instructions on how to get past it.

Acquisition

First things first, you must obtain the key to get inside the Nellis Array. To do so, you must speak to Raquel, a Master-At-Arms of the Boomers. She usually hangs around the Nellis Air Force Base main gate, atop an overturned and barricaded garbage container.

Once you find her, speak to her and ask her about a “bug problem”.

She’ll inform you that the Nellis Array has been taken over by ants who explode when killed with flames, lasers, plasma shots, or explosives. She’ll then ask you to kill all of the ants. Accept the task and go towards the Nellis Array, located north-east of the main gate.

Once there, look for a heavy-duty metal door. Unlock it with the key you received from Raquel and head inside.

You’ll find yourself in a concrete hallway that resembles some of the sewage systems of Vegas. Follow this hallway down until you reach another metal door.

Go through the metal door and head straight until you reach a pile of concrete debris.

If you look to the left, you’ll see a skeleton lying next to a generator. 

Thump-Thump is lying right next to the skeleton.

Comparing Thump-Thump to the Grenade Rifle

• Fires 2x further than the regular grenade rifle. Same as the regular grenade rifle with the long barrel attached. The grenade also has an increased velocity.
  • Due to an error in the code, this only works with regular 40mm grenades.
• Fires slightly faster than the regular grenade rifle thanks to its slightly reduced reload time (2-second reload vs 2.1-second reload) and increased fire rate (2.79 attacks/second vs 2.14 attacks/second).
• Has a 25% increased durability compared to the standard model (620 attacks before breaking vs 495 attacks before breaking).

Usage Tips

• The incredible range and projectile velocity makes this grenade launcher one of the best long-range explosive weapons in the game.
• The explosive damage dealt by this weapon can be nearly doubled by using the Demolition Expert and Grunt (Honest Hearts DLC required) perks.
• Due to the Red Victory and Great Bear Grenade Rifles from the Lonesome Road DLC not benefiting from the Grunt (Honest Hearts DLC required) perk, this grenade rifle has the highest potential damage in the game.