BR55 battle rifle

"When nothing else gets the job done, the BR55 Battle Rifle will do. As the standard gun for all UNSC forces, the BR55 is the easiest gun to pick up and use. Almost all soldiers have trained with it, making its slight defects less noticeable, while accentuating its high rate of fire and accuracy. With both semi-automatic and burst-fire modes, the BR55 is the backbone of all UNSC armed forces."

- Halo Encyclopedia

The BR55 Service Rifle is a UNSC Defense Force infantry battle rifle. It is notable for its powerful three-round burst fire and accurate 2x scope, making it more efficient at farther ranges than the MA5 series assault rifles.

Design details
The BR55 Service Rifle is a gas-operated, magazine-fed, mid-to-long range weapon capable of semi-automatic and burst-firing modes. The BR55, having a rifled barrel, is 89.9cm long and is fitted with a scope for increased accuracy. The scope is mounted on the optics rail. The safety is also located above the handle of the weapon. The weapon fires the M634 X-HP-SAP round from a 36-round magazine. Additionally, the weapon features a scope attachment capable of 2x magnification. In addition to its initial role, the BR55 battle rifle can also fulfill the role of a designated marksman rifle.

XBR55 Battle Rifle
Prototypes of the BR55 existed as early as 2524 and were later used in 2525 during the fall of Harvest. These prototypes lead to the standardized version of the weapon being in service by 2531.

BR55 Heavy Barrel
The weapon's heavy-barreled variant, the BR55 Heavy Barrel Service Rifle, entered service in 2548, superseding the M392 Designated Marksman Rifle, which had been steadily phased out in favor of the BR55, in service in all branches of the military with exception of the Army.

Advantages
The BR55 has reasonably high power, a decent rate of fire, and high accuracy with an electronic 2x telescopic sights attachment; it can be used to deliver three-round bursts at medium ranges. In multiplayer, three body shots and one head shot will kill a fully shielded opponent, assuming the player does not have an overshield. This weapon will kill an unshielded enemy in a single head shot. Target the head and if you're within range a red dot will appear in your reticule. This requires that only one of the three rounds, from a burst, actually hit and kill an enemy. Therefore, it is possible to kill up to three unshielded opponents in a single burst if they are grouped close enough to each other, though this is an uncommon occurrence. However, right after you shoot, it is possible to only shoot one round rather than three bullets, with a melee attack to disrupt the burst. Against vehicles like the Type-46 Spectre or Type-32 Ghost, an experienced player can easily take out the driver, rendering the vehicle immobile, however, this is harder with the Warthog.

In Halo 5: Guardians, the BR55 provides a slightly faster weapon switch and reload time compared to the BR85N. Most notably, however, the BR55 has higher bullet magnetism, which allows targets to be hit with less-than-perfect aim.

Disadvantages
At longer ranges, it is necessary to minimize strafing movements when firing to avoid "splintering" the shot grouping too much. Since each "shot" is actually a three-round burst, certain movements can break up your shot's grouping, and could greatly reduce accuracy. To avoid this, either swap it in for the Covenant Carbine, or get up to medium range. The Carbine has the same degree of firepower, and it lacks the splitting effect although it is slightly less accurate. This also affects accuracy when firing from a moving vehicle such as a Warthog (especially when firing at a 90-degree angle from the vehicle's heading).

The BR55 is not as effective at long ranges. Each bullet also acts as a tracer which gives away the shooter's position. Also, the range is limited compared to the Sniper Rifle. It is also not effective against Sentinels, and does negligible damage against vehicles. Neither is it an effective weapon at close range, as the low fire rate and average stopping power of the weapon makes any fully-automatic weapon far superior in close-quarters combat.

Trivia

 * On the side of the BR55 opposite the charging handle there are two Chinese symbols, "猴王", which translate to "Monkey King".
 * On the level Quarantine Zone in Halo 2, the player can acquire a BR55 from a dead Marine that, when reloaded, can have a total of 236 spare rounds instead of the normal 108 spare rounds.
 * In the Halo 2 E3 Demo, the BR55 was the only weapon shown used in making a melee combo, a feature that was originally meant to be in the final version of the game but was scrapped. It was also shown firing semi-automatically in both the demo and in the E3 2004 Multiplayer Alpha demo, in which the semi-auto mode was engaged when zoomed.
 * The original cover art of Valentine's Exile by E. E. Knight depicts a man holding a rifle. In the original version of the art, this rifle was a render of the BR55 Service Rifle, obtainable at Bungie.net, that was photoshopped to fit in the image. The illustrator, when confronted about it, claimed that he had found the wireframe model in a CD and gave it a generic appearance. The book has since been republished with the figure holding an XM8.
 * Like the sniper rifle, the BR55 is modeled without a trigger in Halo 2.

List of appearances

 * Halo 2
 * Halo: The Cole Protocol
 * Halo Wars
 * Halo Legends
 * Homecoming
 * Halo: Evolutions - Essential Tales of the Halo Universe
 * Dirt
 * Halo: Blood Line
 * Halo: Mortal Dictata
 * Halo 2: Anniversary
 * Halo: Last Light
 * Halo 5: Guardians
 * Know Your Enemy
 * Halo Online
 * Halo Wars 2