BR55 Heavy Barrel Service Rifle

The BR55HB SR Battle Rifle is a UNSC infantry firearm in Halo 3 and is a newer version of the BR55 Battle Rifle in Halo 2.

Design details
The BR55HB SR is a select-fire rifle that has been in service for over 27 years. The UNSC employs the Battle Rifle as a medium range marksman rifle, it fires new 9.5x40mm ammunition from a 36 round magazine, which fits flush in the receiver. The magazine housing is built directly into the underside of the stock of the rifle and is located behind the grip. This titanium alloy weapon is gas-operated with a rotating bolt and therefore must be charged 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, but is pushed back during reloading. The rifle has a housed magazine in the stock. The ejection port is located on the right side of the weapon. The BR55HB SR, has noticeable changes from the BR55. It has a longer barrel for increased range and accuracy. It is also fitted with a Trijicon ACOG-style scope on a modified carrying handle and now also has a trigger guard. The safety is also located above the handle of the weapon.

It is never stated exactly what the maximum effective range of the BR55HB SR is. The MA5C Assault Rifle, which was described as most suited for short to medium range, as opposed to the Battle Rifle's mid to long, has a maximum effective range of 300 meters and the Covenant Carbine, which is similar in use with the Battle Rifle, has a maximum range of 600 meters. It is stated that the Battle rifle could reach up to 900 meters with deadly accuracy; however, that may have been due to the design of the prototype Battle Rifle, deployed in 2524, the field issued Battle Rifle may not have that type of range. .

Ammunition
The BR55HB SR uses a 9.5x40mm M634 X-HP-SAP. Even when fired in three-shot bursts, the round produces little recoil resulting in nearly no muzzle lift. The rifle's ammo is more effective against both shielded and unshielded Covenant infantry than the 7.62x51mm NATO used in the MA5C Assault Rifle, as the increased accuracy leads to an increased amount of headshots the marksman can place on a target, and the increased kinetic energy of the round leads to faster shield depletion and increased damage to unshielded enemies.

Advantages
The BR55HB SR has reasonably high power, a decent rate of fire, and high accuracy with its 2x magnification scope. Its range is its primary advantage, allowing the rifleman to engage at longer ranges by leading shots. The BR55HB SR has a slightly lower recoil then its BR55 predecessor and has less muzzle flash, although the rounds fired are still visible in the air; the rifle's updated design also boosts range and accuracy, increasing the effectiveness of the 9.5mm rounds it fires. The scope of the BR55HB SR allows a skilled marksman to easily take down an unshielded target from medium range, making the battle rifle the best alternative to the high powered sniper rifle system that the UNSC provides for its marksmen.

Disadvantages
Attempting to engage a target at longer ranges requires more rounds and less movement as the rounds become inaccurate over longer ranges, and its magazine can be depleted rather quickly. The weapon requires a good amount of skill in order to use it. The user must have an understanding of how the weapon works, and what to do with it when a situation arises. Each bullet fired from the weapon can act as a tracer, and can give away the shooter's position, putting him at risk of return fire. While effective at long range against light or unshielded targets, the BR55HB's performance against shielded infantry at close range, is extremely challenging; the BR55HB while still very effective, is not the weapon of choice at close range because of its design.

Influences
The most obvious (though false) inspiration for the shape and design of this rifle is the French-made FAMAS assault rifle. They are externally nearly identical in design, featuring a bullpup configuration (the magazine and receiver behind the trigger) and a skeletonized carry handle. However, the FAMAS is an assault rifle, firing a 5.56 x 45mm intermediate round, and the BR55HB SR is a battle rifle, firing a fictional 9.5 x 40mm round. A Bungie staff member said they did not know of the FAMAS assault rifle, and were worried people would think they had copied it.

Yet another key inspiration for the BR series was the German-manufactured G36 line, particularly in the area around the carry handle and rail system. In its handguard, it also bears influence from another German design, the XM8 which was derived from the G36 and slated to become the new standard service rifle for the United States military prior to its cancellation.

Changes from the BR55 in Halo 2

 * Modified optical rail
 * New Trijicon ACOG-style scope
 * New trigger guard
 * Longer barrel
 * New reloading animation
 * Less aim-assist/magnetism, harder to aim
 * Slightly different firing sound
 * Slightly lower rate of fire
 * Decreased accuracy/greater spread
 * Slower rounds - no instant hit anymore, so leading shots are needed from longer range.

Tactics
An important thing to note is that the BR55HB SR can be used to great effect at medium to long range. The trick with making the Battle Rifle effective at long range is minimizing the operator's side-to-side movement. Strafing while firing greatly decreases the efficiency of the rifle. Additionally, while firing at a moving target it is important to aim in front of the target, especially when the target is moving perpendicular to the aim of the rifleman.

Campaign

 * The BR55HB SR Battle Rifle is a marvelously effective weapon against all types of enemies, from Grunts to Brutes and even Flood, if you're a good marksman. When engaging Brutes, always remember to aim center of mass until the power armor is disabled, then aim for the head. When engaging Flood aim for the center of the combat form as taking out the infection form in the chest cavity will kill it.
 * For targets on foot, it is optimal to aim 0.75-1.00 head-widths in front of the target to guarantee the maximum possible number of rounds impact the target. For targets in vehicles, it is ideal to aim 1.75-2.5 head-widths in front of the target. Attempting use of a BR55HB SR Battle Rifle against vehicles at great range is not advised. Odds are the vehicle you are trying to take down is not an immediate threat that the rifleman needs to eliminate and he should shift his focus to a more readily available target, for instance, infantry like Grunts.

Multiplayer

 * In multiplayer, it takes four headshot bursts to kill a fully shielded SPARTAN-II or Elite, or three body shots followed by a headshot (head shots are only necessary to kill unshielded opponents; the bullets do equal damage on any part of a shielded body).
 * Another use of the BR is to melee(beat down), then get a headshot for an instant kill. This is much more effective than shooting then meleeing, seeing as this would take at least three bursts before the melee would kill the opponent. This is much less effective than in Halo 2, when there was a button glitch which made it much easier. The method is not recommended unless they are unaware of you, because you may get hit back if they fired first and die.
 * In multiplayer (preferably Team SWAT), you can "twitch fire" the rifle so that you can execute an easy headshot. The way it can be executed is such, just when you fire at mid-lower chest area of your target, "twitch" the reticule upwards and the three bullets will separate, thus decreasing its accuracy but creating a greater headshot hit box.

Advanced Tactics

 * A well-known tactic known as the "Noob Combo" or as the "EMP combo" is to use an overloaded Plasma Pistol shot to remove the shields of an opponent, then immediately follow this hit with a head shot to kill the opponent.
 * Another useful Battle Rifle tactic is to use a Sniper Rifle shot to reduce the shields of a target, then switch to the Battle Rifle for an easier headshot. This is more useful at long ranges, where the opponent has a CQB or a slow explosive weapon. This tactic is better for inexperienced snipers to use, as it uses less ammunition than two sniper body shots.
 * Arguably, the best equipment combination with the Battle Rifle is the Power Drain. By throwing down the Power Drain, the shields of your enemies are instantly brought down, thus allowing for an easy one-shot kill with minimal ammunition usage. This is more suited for ambushes, as it takes a few seconds to deploy the power drain. The power drainer is especially useful on levels that involve lifts, for example Construct. As mentioned previously, a Frag Grenade can be used in its place, for example on Guardian.

Trivia

 * The "HB" most likely is an acronym standing for "Heavy Barrel", which indicates the lengthened barrel of this rifle and the weighty barrel on the stock. "SR" could stand for "Scoped Rifle", which is simply an additional description of this weapon.
 * Sometimes the Battle Rifle will have one or two extra rounds, causing a half burst. This is caused by retrieving ammunition from a marine A.I.
 * The Marathon symbol is located on the gun's left side, to the left of the ammunition counter display and roughly above the trigger guard and on the stock.
 * WETA Studios made a replica Battle Rifle, along with a Magnum, Sniper Rifle, Carbine, Gravity Hammer, Spike Grenade, Rocket Launcher, and Plasma Pistol to use in the currently "on hold" Halo film.
 * During Halo 3's development, Bungie did many calculations and tests, in order to make sure the Battle Rifle and Assault Rifle were evenly balanced.
 * The Battle Rifle is the starting weapon of choice in Major League Gaming, a professional video game league that includes Halo.
 * The Battle Rifle would be best suited as a DMR (Designated Marksman Rifle) due to the limited amount of ammunition that can be carried by an individual Marine, ODST, or Spartan.
 * The Battle Rifle, along with the Elite Plasma Rifle and the Energy Sword, does not return in Halo 3: ODST; except for a small cameo. It is gameplay-wise replaced by the M6C/SOCOM.