For an overview of Gatling laser models in the Fallout games, see Gatling laser.
“An H&K L30 Gatling Laser. Designed specifically for military use, these were in the prototype stage at the beginning of the War. Multiple barrels allow longer firing before overheating. Powered by Micro Fusion Cells.”— In-game description
Designed specifically for military use, the L30 was in the prototype stage at the beginning of the Sino-American War. Capable of firing only in burst and with a low energy capacity, it was eventually superseded by the more advanced full auto Gatling.
Commonly regarded as the ultimate energy weapon, the L30 saw use (post-War) by Brotherhood of Steel Paladins, UnityNightkin, and even Enclave soldiers. On that note, advanced power armors have a 90% resistance against laser damage, which means the user has to rely solely on critical hits to deal significant damage against enemies in any sort of metal or power armor. However, if one has tagged Energy Weapons from the start, and picked the right perks, the Gatling laser can be both very devastating and economical due to the popularity of ammo in the later part of the game, along with high per-shot damage and canceling armor AC/DR due to each shot being critical (Fast Shot trait, Better Criticals perk, Sniper perk combined with 10 Luck).