Swarm LRM

Swarm LRMs are an alternate Long Range Missile type.


The Swarm missile was developed in 2621 as part of an attempt by the Terran Hegemony to replace fragile and sluggish standard artillery pieces with sturdier and more mobile BattleMechs with specialized LRMs. The Swarm missile was intended to recreate the splash damage ability of artillery shells.[1]

Missiles from a Swarm salvo that miss the intended target then attempt to home in and strike at any adjacent targets, helping to break up enemy formations. Ignoring its higher cost, the Swarm missile never became more than a specialty loadout because the missiles, like artillery, indiscriminately target any nearby unit, whether friend or foe.[2][3]

Swarm LRMs fell out of favor among the Successor State militaries as the technological decline of the Succession Wars forced 'Mech combat into shorter and shorter ranges, increasing the odds of friendly fire strikes, before the technology itself was ultimately lost in 2833. Swarm LRMs were another technology retained by the Clans, who used it to leverage their range advantage and preference for avoiding close range combat to great effect. Inspired by having it used against them, the Federated Commonwealth's New Avalon Institute of Science reintroduced the standard Swarm LRM to the Inner Sphere.


The Free Worlds League worked at overcoming their indiscriminate nature by adding an IFF (Identity Friend or Foe) detector to the missiles, producing the so-called Swarm-I.[4][3] The Swarm-I is roughly similar to conventional Swarm missiles, but includes an IFF (Identification: Friend or Foe) detector so as to target only enemy units. However this modification is not foolproof, with the chaotic nature of the modern battlefield throwing up conflicting signals, active ECM Suites blocking the detector outright and damage to a friendly 'Mech or Combat Vehicles electronic systems preventing the broadcast of an IFF signal will cause a Swarm-I missile to act identically in such instances to a standard Swarm with all the drawbacks.[3]

It is unknown whether or not the Clans have produced their own version.[3]


The Swarm LRM missile munition has only been featured in one video game - MechCommander 2. The in-game weapons function in a different fashion than as described above; the missiles target the ground and create a small shockwave like one would expect from thermobaric artillery shells. Additionally, it is only available as an LRM-5 Rack alternative rather than an alternate munition, and features slightly different statistics in comparison to its regular LRM counterpart.[citation needed]


Swarm and Swarm-I missiles are compatible with standard LRM and MML systems.[3]

One ton of Swarm missiles cost twice as much as standard LRMs.[5]

One ton of Swarm-I missiles cost three times as much as their standard LRM counterpart.[5]

Swarm and Swarm-I LRMs function as standard LRMs but after rolling on the cluster hit table to see how many Swarm LRMs hit the target, any leftover Swarm LRMs act as a new attack on other units in the same hex as the original target. If an LRM-15 of Swarm munitions shows 9 missiles hit a Charger in a hex, then the remaining 6 missiles are treated as a new LRM attack of 6 missiles against a Pegasus hovertank in an adjacent hex. The cluster hit table for the Pegasus uses the 6 column in this example. Moreover, if the initial attack on the primary target failed, the Swarm LRMs automatically move to any new targets in the same hex or immediately adjacent hexes. This is handled as a secondary attack.[6]

Swarm-I missiles follow these rules, but add a +2 to hit modifier when they target a friendly unit, making it harder to hit said unit. If the missile flight is affected by a hostile ECM field, Swarm-I missiles act as Swarm missiles and Swarm missiles act as standard LRMs.[6]


  1. TechManual, p. 231: "Swarm LRM"
  2. Technical Readout: 2750, p. 9: "Swarm LRMs"
  3. 3.0 3.1 3.2 3.3 3.4 TechManual, p. 231
  4. Field Manual: Free Worlds League, p. 137: "LRM Special Munitions"
  5. 5.0 5.1 TechManual, p. 295
  6. 6.0 6.1 Tactical Operations: Advanced Units & Equipment, pp. 182–183