Mark 2555 heavy railgun

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Mark 2555/20cm heavy railgun
Artwork of an Mark II [J Colossus]] from above.
The Mark 2555 railgun mounted on the left shoulder of a Colossus.
Production overview


Heavy railgun[1]


Ammunition type:

20cm rounds[1]

Service history

In service:

Post-Covenant War conflicts (presumably 2555-present)


The Mark 2555/20 cm heavy railgun (HRG) is an electromagnetically-operated heavy artillery piece in the service of the United Nations Space Command.[1]


Design details[edit]

The Mark 2555 follows the older Mark 2547 model, operating as a heavy railgun. The weapon was originally designed to fire from a fixed position, and was intended to be mounted atop static structures and fortifications.[2] However, they have since been installed on the modular hardpoints of the HRUNTING/YGGDRASIL Mark II (J) Colossus walker, with the vehicle's most common configuration mounting a Mark 2555 on the left shoulder, above the M193LP autocannon. In this configuration, the weapon is capable of targeting only ground units.

The Mark 2555 railgun fires a 20 cm slug from its rails, and is considered a long-ranged weapon.[1]

Operational history[edit]

Based on its model designation, the Mark 2555 presumably entered service in the eponymous year of 2555. It was used by the forces of UNSC Spirit of Fire in the Second Ark Conflict in 2559. During the war on the Ark, multiple Colossi sporting Mark 2555 HRGs were used during Operation: SPEARBREAKER.[3]


List of appearances[edit]


  1. ^ a b c d Halo Encyclopedia (2022 edition), page 146
  2. ^ Halo Wars 2, Phoenix Logs: Colossus
  3. ^ Halo Wars 2, campaign level Not On My Watch