40px-Terminal.png This article, BR55X Battle Rifle, was written by Spartan 501. Please do not edit this fiction without the writer's permission.
BR55X Battle Rifle
Production information





Battle Rifle

Technical specifications

Two Hand

Damage Per Hit


Magazine Size

60 Rounds

Maximum Ammunition

600 rounds or 10 magazines

Fire Mode

3 Rd Burst, Full Automatic, Semi-Automatic

Ammunition Type

M634 9.5mm x 40mm X-HP-SAP (Experimental, High Penetration, Semi-Armor Piercing)


Short-Stroke Gas-Operated Rotating-Bolt








BR55 Battle Rifle, BR55HB SR Battle Rifle






The BR55X Battle Rifle was a prototype weapon for the BR55 Battle Rifle, used during the Battle of Harvest by Seargent Avery J. Johnson and select members of the colonial militia that defended the planet. The weapon was in development by ONI, and featured a 60 round magazine, laser pointer, and several modes of fire, not just three round burst mode.

Physical Description

The BR55X is a bullpup, fully automatic, UNSC rifle that fires the 9.5x40mm X-HP-SAP round. It fires from a 60 round magazine which fits flush in the receiver. The receiver is built directly into the underside of the butt of the gun and is located behind the grip (known as a bullpup configuration).

This titanium alloy weapon is gas-operated with a rotating bolt and therefore must be cocked before the first round can be fired. The charging handle used to chamber the round is located on the left side of the weapon and does not move during operation. Once the first round is fired, the gases from that round and those to follow impinge upon a gas piston, which pushes back the bolt carrier, rotating the bolt inside and continuing to chamber rounds until the magazine is empty. Once the magazine is empty, the charging handle can either be pulled back and locked or, it can be fully cycled after a fresh mag has been housed. If it is pulled back and locked, then it must be pushed forward once a fresh magazine is housed to chamber a new round. The magazine release button is located on both sides of the gun with an arrow pointing down towards the housed mag in the stock. The ejection port is located on the right side of the weapon. There is also a fire selector on both sides of the ammo display.

The BR55X strangely bears more resemblance to the BR55HB SR than the earlier BR55. It has an optical scope identical to the BR55HB SR, and has a trigger guard, something the BR55 lacked. In addition, it has a rifled barrel, as well as a longer one than the BR55. The BR55 has a few internal differences from the BR55, such as a 60 round magazine instead of 36, and selective fire, instead of just the three round burst mode.


The BR55X started development in 2512 under a cloak of secrecy, during the prime of the Insurrection. The MA5 rifles that were being used were largely ineffective, and while the UNSC had other weapons, such as the M7 SMG, it needed a good, solid, workhorse weapon that it could laud and publicly announce as the successor of the MA5. During development, some major goals were assessed. One was to give the weapon range, accuracy, and stopping power, all three things that the MA5 lacked. Another was to make the weapon perform exemplary with an ACOG style scope.


  • 60 round magazine
  • Selective fire
  • Higher recoil
  • Increased jamming

Field Usage

The BR55X saw action in a limited spectrum of the military, but due to its high advances in technology for the time, it had several users. The first recorded use in combat was during the battle of Harvest, where it was used by Staff Seargents Avery J. Johnson and Nolan Byrne, as well as members of the Harvest militia like Wallace A. Jenkins. Later on it, was used by many soldiers with ties to ONI Section III, the part of ONI who created the weapon. One group, the SPARTAN-Xs, used the BR55X with frequency.


The BR55X, since it was a testbed model, had a number of flaws in its design. Due to insufficient recoil dampening, it had higher recoil than the standard BR55, which was something that was corrected in later models. Another flaw was that it would spontaneously jam, due to loss of spring strength in the mag. This too however, was corrected in later models.


"I see real potential in the bee are fifty five exx, provided the brass can change some things around and fix some of the flaws that have plagued the model since it's inception."

"The consistent jamming of the (BR55X) is frustrating. It is nice to have such a large clip, but I really don't think that having one out of every four clips be defective is worth it."

"I can definitely see the bee are fifty five exx (BR55X) becomming a mainstream weapon, its already gathering good remarks and positive reviews."

"The bee are fifty five exx (BR55X) has a nice concept, and is better than the em eh five bee (MA5B) at most mid ranged and ranged combat. Recoil is a little high, but nothing that you can't compensate for."