BR55 battle rifle

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.

Overview
"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 gas-operated, magazine-fed, mid-to-long range weapon capable of semi-automatic and burst-firing modes. Prototypes of the BR55 existed as early as 2524 and were later used in 2525 during the fall of Harvest. The standardized version of the weapon was in service by 2531. 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. The weapon fires the M634 9.5x40mm X-HP-SAP round from a 36-round magazine, though the heavy-barreled variant utilizes the 9.5x40mm KURZ. Additionally, the weapon features a scope attachment capable of 2x magnification.

This titanium alloy weapon is gas-operated with a rotating bolt. Therefore, the charging handle must be racked before the first round can be fired; this will chamber a round and lock the breech, sealing the round inside. The charging handle used to chamber the round is located on the left side of the weapon and does not reciprocate. Once the first round is fired, the gases from that round—and those to follow—impinge upon a actuator rod (otherwise known as an op rod), which pushes back the bolt carrier, rotating the bolt inside which unlocks the chamber and initiates the extraction of the spent cartridge. As the bolt carrier group cycles to the rear, the spent casing is ejected from the weapon, and another round is chambered, 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 magazine 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 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.

Ammunition
The weapon fires the 9.5 x 40mm experimental round. The 7.62 x 51 mm NATO round is a rather high-powered round used on the MA5 and on modern-day marksman rifles and machine guns. The 7.62 mm already has a history of having too much recoil in smaller, lighter weapons, which makes it hard to control in full-auto. Despite the shorter case size of the 9.5x40mm cartridge, the increase in diameter would actually slightly increase the amount of powder present. The level of recoil would be enough to drastically decrease accuracy and inhibit the ability to fire controlled bursts for Marines, although for Spartans it should not be a problem, and this might be mitigated by the BR55's design.

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 Spectre or Ghost, an experienced player can easily take out the driver, rendering the vehicle immobile, however, this is harder with the Warthog.

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.

Campaign

 * The BR55 is the all around go to weapon when facing Covenant forces, as it can effectively take down Grunts and Jackals with one well placed three shot burst to the head (torso shots require about two to four bursts to kill).
 * Given that the bullets bounce straight off a Jackal's Energy Shield, fire a well-placed shot through the small notch on the shield's right, and, as the Jackal recoils from the wound, finish it off with a head shot.
 * Elites' energy shields are very resistant to the BR55. Try to keep the rifle leveled at its head and keep firing until it falls dead. It is advisable to soften an Elite up with grenades, melee attacks, or a Plasma Pistol's charged shot before engaging them with a BR55, especially on higher difficulties. On higher difficulties, the Plasma Pistol/Service Rifle Combo is extremely efficient, as it only requires one overcharge and a headshot against any Elite.
 * In Halo 2, you can kill a Brute with three head shots, as the first two bursts will knock off the helmet, and the following headshot will kill the Brute. However, shooting a Brute in any other area is not particularly effective due to their extreme resilience (on Heroic it takes about 17 3-round bursts, or one and a half magazines, to bring down a Brute).
 * When engaging a Hunter, dodge behind them, firing as many bursts as possible into their exposed orange sections before they turn around.
 * The BR55 is somewhat limited against the Flood, however, a 3-round burst to the center of a Combat Form's chest where the Infection Form is will generally destroy it.

Multiplayer

 * The BR55 replaces the M6D from Halo: Combat Evolved. Most of the tactics remain the same; however, you do not need to lead your shots as much as the M6D due to the fact that the BR55 relies on a hitscan mechanic.
 * The BR55 paired with the Plasma Pistol makes a good combo. Paired with an SRS99C-S2 AMB Sniper Rifle the battle rifle will fill the gap of medium to long range.
 * There is a playstyle known as the "four-burst tactic": three to the body and one to the head, As long as the opponent doesn't have an Overshield, and/or any other in-game health bonuses.

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.

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