The M57 Pilum was designed to replace the older M41 rocket launcher, which was considered obsolete by the end of the Human-Covenant war. Compared to the older M41, the M57 deals the same amount of damage while being cheaper to produce and substantially lighter. Instead of being fed by pre-loaded disposable tubes, the M57 is fed by a reusable box magazine which can hold up to 2 50x137mm HEMP rockets.
A Pilum is a roman spear, yet another incorporation of greek, roman, and norse history.
The M57 rocket launcher can be found in the following Arena multiplayer maps: