The Vault - Fallout Wiki

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The Vault - Fallout Wiki
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For an overview of the M42 "Fat Man" Launcher throughout the Fallout series, see Fat Man.
Big Boy
Fo4 Fat Man.png
TypeHeavy weapon
Damage2*450 damage in a 4.28 m (14.06 ft) radius (12.14 m (39.82 ft) total)
Damage TypeBallistic
Ammo TypeMini nuke
Ammo Cap.1
Attack Rate1
314.16 m (1030.71 ft) (maximum projectile range)
AccuracyNot applicable
Special Effects
Fires an additional projectile
Weapon Modification
Weapon VersionsFat Man
The Striker
Editor IDAspiration_Weapon_DC_Fatman
Base ID0021a53e

Big Boy is a unique weapon in Fallout 4.


The following section is transcluded from Fat Man. To modify, please edit the source page.

The M42 Fat Man was developed at Fort Strong near Boston, Massachusetts. Development began in February 2076, with the goal being the development of a man-portable tactical nuclear launcher easy enough for use by troops on the ground, to destroy reinforced and entrenched positions.[1][2] Problems manifested instantly, as warheads were simply too heavy to clear the blast radius fast enough to provide safety for the operator. Even stripping them to the minimal possible size failed to produce an acceptable effect. Instead, the development team decided to increase the power of the launcher unit, even considering using railgun technology to accelerate the warhead. The notion was largely academic, as it would require for the overburdened soldier to carry an additional power pack the size of a suitcase and turn the Fat Man into a crew-served weapon.[3] Concurrent development ran on the MIRV version of the launcher. Live-fire testing claimed lives, in fact, with two soldiers killed during a test. No remains were recovered and the commanding officer in charge of the project, General Brock, covered up the incident, ordering his subordinates to send sand packed in an urn to their relatives.[4]

The project hit a breakthrough in December 2076,[5] when the project lead discovered a solution for the launcher problems. Six hours, fourteen cups, and one concerned night shift lab crew later, the future M42 launcher was conceptualized: Based on the spigot mortar mechanism, the launcher would only have to accommodate a firing through and system, relying on mechanical launching, rather than chemical or electrical means. Much like the 130 year old PIAT launcher, the Fat Man warhead would be propelled by a sub-charge embedded inside the warhead, "catapulting" the warhead through the air to the target - giving plenty of range with the added bonus of not producing a smoke trail that could reveal the firing team to the enemy.[6]

By September 2077,[7] after one hundred test firings the weapon were complete and ready to be shipped to units overseas. A large number of units was manufactured and shipped together with the appropriate warheads to select locations throughout the United States.[8]


The standard M42 "Fat Man" Launcher is a man portable nuclear payload, anti-materiel weapon platform. It can contain a single mini nuke only.

A modified variant of the standard M42 Fat Man, the Big Boy fires 2 mini nukes per shot for the price of 1, for an incredibly devastating volley. Remember to duck and cover after firing.



Slot Damage Fire Rate Weight Value Resources Required Perks
Standard Base +2.5% +2.5% 4x Adhesive
6x Aluminum
6x Gear
4x Nuclear Material
5x Screw
6x Spring
9x Steel
MIRV Launcher Multiple projectiles dealing 450 damage in a 3.43 m (11.24 ft) radius (9.28 m (30.45 ft) total)


+25% AP cost +20% +30% 9x Adhesive
11x Aluminum
5x Circuitry
8x Gear
6x Nuclear Material
8x Screw
7x Spring
Gun Nut 4
Science! 4