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For an overview of this weapon in the Fallout series of games, see Fat Man.

The Fat Man is perhaps the most devastating infantry weapon ever unleashed upon the modern battlefield - a hand-held catapult that launches portable nuclear bombs.

— VDSG Catalogue No.9716

The M42[1] Fat Man is a weapon in Fallout 4.


First entering service in September 2077 with the U.S. Army, the Fat Man is a shoulder mounted mini nuke launcher. The variant appearing in Fallout 4 has a slightly different appearance than in previous games. There is no longer a handle on the right side of the launcher, and instead two straight handles on the bottom. It also appears to be larger, with a rusted silver paint job.

Developers struggled to find a way to fire the heavy ammunition from a man-portable system far enough to keep the operator outside the blast radius, losing a lot of people in the process. Eventually, it was discovered that by placing a small sub-charge into the ammunition itself, similar to bullets being fired from a gun (or perhaps more accurately described as being along the lines of a recoilless launcher), the warheads could be launched a considerable distance without adding too much weight to the already heavy weapon.

When fitted with the MIRV launcher, it fires six mini nukes in a cluster that separate in midair, drastically reducing its range, but increasing its overall damage and area of effect.

Weapon modificationsEdit

Slot Mod Description Weapon prefix Damage per shot changeIcon damage Fire rate changeIcon attack Range change Accuracy changeIcon spread Magazine capacity (shots per reload) changeAssault carbine extended magazines Weight changeIcon weight Weapon value change in capsIcon merchant Perk needed Components Base ID
Launcher Standard launcher Standard. Adhesive x4
Aluminum x6
Gears x6
Nuclear material x4
Screw x5
Spring x6
Steel x9
MIRV launcher An experimental modification. Experimental MIRV -450 +5.3 +138 Gun Nut 4
Science! 4
Adhesive x9
Aluminum x11
Circuitry x5
Gears x8
Nuclear material x6
Screw x8
Spring x7



  • Robotics Disposal Ground - Found laid on top of a car hood near the back of the scrapyard.
  • Chance of being equipped by raiders with power armor.
  • Fort Hagen - In the armory.
  • Revere satellite array - Can be found at the top of one of the towers, next to a power armor frame and a case with miscellaneous ammo and other items.
  • Malden center - Found behind a train car hugging against a wall.
  • BADTFL regional office - In the evidence locker.
  • Goodneighbor - Found behind the desk, beside KL-E-0 in the Kill or Be Killed store.
  • ArcJet Systems - Found in the room marked '2' in the Engine core.
  • Federal ration stockpile - In the main stockpile area, just inside the room with two turrets against the wall near the terminal that operates the doors (second one). This Fat Man also respawns.
  • Lexington - On the walkway where the Raider with the power armor is found.
  • Quincy ruins - being held by Sergeant Baker, who is located on top of the church in the ruins.
  • Boston mayoral shelter - Beneath the basketball court is an entrance to a cave. The Fat Man lies next to a dead soldier at the end of the cave. There is a nearby deathclaw that will attack on sight, so early on, this should be avoided until you are at a higher level.
  • D.B. Technical High School - At the far end of the old swimming pool in the northwest corner of the lowest level of the school. This is by the raider boss' bed and terminal.
  • Cabot House - In the basement near Edward's bed.
  • Boston Airport - Slightly north of Boston Airport, there are wrecked cars. Inside one is a Fat Man. From the Boston Airport fast travel location proceed East. The nose section of an airplane will be in front of you. The Fat Man is located in a van on the water's edge behind the nose section.
  • Salem - On a shelf in a bombed out store across from the chapel.
  • The Castle - Found in the armory on a shelf, next to it will be a mini nuke.
  • Spectacle Island - On the lower level of the beached tugboat containing the generator.
  • The Prydwen - Inside Proctor Teagan's store.
  • Gunners plaza - In a locked utility closet in the south-west corner of the second floor.
  • Libertalia - Carried by a random raider at the top of the main building.
  • Hub City Auto Wreckers - Carried by a named Gunner, Bridget.
  • Zephyr Ridge Camp Far Harbor (add-on)Gametitle-FO4 FH - Carried by a trapper on the tower's top level.


  • There is a chance that a mini nuke fired by the Fat Man will be a dud and cause physical damage instead to the target, if hit by the dud.[2]
  • Technical documentation and holotapes found in Fort Strong reveals the Fat Man's pre-War designation: 'The M42 Fat Man'.
  • The Fallout 4 Fat Man appears to have a slightly smaller blast radius than the Fallout 3 version.[verification needed]
  • When fired from a long enough distance, the projectile makes a loud whistling noise (similar to the cartoon noise for falling from the sky) which indicates one should get to cover ASAP or sprint away.
  • Preston Garvey dislikes using the Fat Man presumably because of its destructive nature.
  • When firing with the experimental MIRV modification, there's a chance that it will detonate right at your feet, even if you are firing away from yourself.
  • During the first scene of the game, the player can see an advertisement for the Fat Man playing on TV.

Behind the scenesEdit

50 Vault-Tec C.E.O.The following is based on unverified behind the scenes information and has not been confirmed by canon sources.
  • The Fat Man may have been inspired by the real life M-28/29 "Davy Crockett", which was deployed with American soldiers in the Cold War. The main differences are that the Davy Crockett was fired via tripod, while the Fat Man is shoulder-fired, much smaller/lighter and its mini nukes have a significantly smaller yield than the Crockett's.[3]
  • The Fat Man could only exist in its form if it used the Isotope Californium-252, due to its low critical mass, which is the mass necessary to start a nuclear fission reaction. Though it would have been incredibly expensive to mass produce them since a microgram (one millionth of a gram) of Californium 252 costs 10$ and you would need around 2.73 kilograms (5.95 pounds) per mini nuke.
50 Vault-Tec C.E.O.End of information based on unverified behind the scenes information.





  1. General Brock's terminal in Fort Strong and Private Murnahan's holotape found in Fort Strong refer to the Fat Man as an "M42 nuclear catapult"
  2. Ten things we've learned about Fallout 4 - Tech Radar
  3. Davy Crockett on Wikipedia.