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The experimental MIRV is a weapon in Fallout 3.


The experimental MIRV is a unique Fat Man that can be found in the bomb shelter area of the National Guard depot. This weapon deals the most damage of any weapon in the entire game, as it acts like a shotgun version of the Fat Man, delivering eight mini nukes at once. The MIRV actually does the same damage as a Fat Man per mini nuke, as 12 880/8 equals 1 610. It will not fire if the Lone Wanderer doesn't have at least 8 mini nukes in their inventory to load it with. If they have fewer than 8 mini nukes, the weapon will reload but never discharge the payload.


The Experimental MIRV can fire a total of 63 shots, the equivalent of 504 mini-nukes, from full condition before breaking.


  • Fat Man - The common variant in Fallout 3.


Weapon name (current weapon is highlighted)- Weapon name (melee or unarmed)Attacks in V.A.T.S.- Attacks in V.A.T.S.
Weapon name (current weapon is highlighted)- Weapon name (gun, energy or explosive)Action point cost- Action point cost
Damage per attack (damage per projectile)- Damage per attack (damage per projectile)Damage per action point- Damage per action point
Damage per second- Damage per secondWeapon spread- Weapon spread
Area of effect damage- Area of effect damageMagazine capacity (shots per reload)- Magazine capacity (shots per reload)
Effect damage & duration- Effect damage & durationDurability (number of attacks before breaking)- Durability (number of attacks before breaking)
Bonus effects- Bonus effectsWeight- Weight
Attacks per second- Attacks per secondValue in caps- Value in caps
Critical chance % multiplier- Critical chance % multiplierValue to weight ratio- Value to weight ratio
Critical damage- Critical damageSkill required- Skill required
Critical effect damage & duration- Critical effect damage & durationStrength required- Strength required
With all mods attached- With all mods attached
Weapon name (current weapon is highlighted)Damage per attack (damage per projectile)Damage per secondArea of effect damageBonus effectsAttacks per secondCritical Chance % multiplierCritical damageAction Point costDamage per action pointWeapon spreadMagazine capacity (shots per reload)Durability (number of attacks before breaking)WeightValue in capsValue to weight ratio
Fat Man 10
25421600+10 Radiation/12s1.58x006524.82.0116730100033.3
Experimental MIRV 80
20336.212800+80 Radiation/12s1.58x0065198.213.08(1)6330249883.3


The player must complete the unmarked quest Keller Family Refuge before they can gain access to the secure section of the depot housing the weapon, though it's also possible to gain entrance to the armory by using a glitch. See the bugs section on National Guard depot for more details.


  • The MIRV looks identical to the Fat Man, meaning only one mini nuke appears to be loaded on to the weapon; however, the game overlaps all eight mini nukes, which separate upon exiting the weapon.
  • Sometimes the MIRV (or Fat Man), is set up such that using it in V.A.T.S. will cause the player character to aim directly at the enemy, without aiming upwards to compensate for the distance or mini nuke drop. This, coupled with the fact that only the 8th nuke shot out of the MIRV will go as far as the Fat Man's single nuke (and all other nukes will travel shorter distances), means that using the MIRV in V.A.T.S. will usually cause the player character's death.
  • If the player character looks directly at the ground and fires the MIRV, the 8 mini nukes' combined power is enough to launch their dead body to the height limit.
  • Similarly, the MIRV can potentially send the bodies of human enemies hit by multiple mini nukes flying hundreds of feet into the air, potentially rendering their bodies impossible (or very hard) to find.
  • It costs more to fire this weapon once than it does to repair a regular Fat Man twice. At several hundred caps per nuke and firing eight nukes per shot, this is the most expensive weapon in the game, albeit the most powerful.
  • Out of every weapon in Fallout 3, the MIRV is the most powerful in terms of base damage.

Behind the scenes

MIRV is a military term for Multiple Independent Reentry Vehicle. It is a collection of nuclear weapons carried on a single intercontinental ballistic missile. Using a MIRV warhead, a single launched missile can strike several targets, or fewer targets redundantly.


  • Xbox 360Xbox 360 Sometimes a graphics error can occur when detonation is very close. It can cause large, black rectangles to extend from the weapon out to as far as you can see. A console restart will fix this. [verified]
  • PCPC Xbox 360Xbox 360 Sometimes when lifting the item, it will twirl around in the air. [verified]
  • PCPCIf you equip the weapon and enter V.A.T.S. while having less than 8 Mini nukes, V.A.T.S. will not show you the "not enough ammo" box, but if you actually try to use it the weapon will not shoot and you will get stuck in the V.A.T.S. sequence, reloading a save will fix the problem. [verified]
  • PCPCThere is an extremely rare chance, that a Fatman with the Experimental MIRV modification will spawn in a safe, this is likely an unexplained bug as the Creation Kit shows no indication of the Experimental MIRV implemented onto any leveled loot lists.[verification needed]


SingleShotVB.png ReloadVB.png