It was first unofficially introduced late in the Battle of Harvest. The exact year of when they were first used is unknown, but it was noted by a UNSC Lieutenant Colonel in a document in 2530 that "Marines have improvised during the fight here [on Harvest], and improved their BR55s by adding on crudely made silencers to the end of the muzzle. They work well, and I recommend that a custom variation to the BR55 be designed with an either permanent or removable silencer.".