BR55 Heavy Barrel Service Rifle

The BR55HB SR Battle Rifle is a United Nations Space Command infantry firearm, a variant of the BR55 Battle Rifle, and a service rifle of the UNSC Marine Corps.

Introduction
The BR55HB SR Battle Rifle is a gas-operated, magazine-fed, mid-to-long range weapon capable of 3-round burst or fully automatic fire. The modern successor to the BR55 Battle Rifle, the BR55HB SR remains relatively unchanged, firing the M634 9.5x40mm X-HP-SAP round from a 36-round magazine, and equipped with a 2x electronic scope for better accuracy at longer ranges. The BR55HB SR, however, is capable of automatic fire as well, and appears to have a slightly longer barrel than its antecedent. The penetrative power, accuracy, and range of the BR55HB SR is roughly equivalent to the BR55, although its accuracy has slightly decreased from it's earlier counterpart.

The BR55HB SR Battle Rifle appears to be one of the service rifles of the UNSC Marine Corps, and is the standard-issue for fewer Marines than the more commonly seen MA5C Assault Rifle, which is the standard issue for almost every marine. While the BR55HB SR offers greater range and accuracy than the MA5C, the MA5C is easier to handle in a close-quarters engagement. The characteristics of the BR55HB SR are comparable to the Covenant Carbine, although the mechanisms and aesthetics of the two weapons differ greatly.

Advantages
The BR55HB SR Battle Rifle 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 which may be out of range for the MA5C. The BR55HB SR's accuracy and penetrative power make it a useful weapon to kill unshielded opponents: a single headshot with the 3-round burst instantly kills Grunts and Jackal Snipers, unshielded Elites and Brutes at medium range. In multiplayer, it takes four headshots to kill a fully-shielded SPARTAN-II or Elite, and seven body shots. This has led to a well-known tactic colloquially known as the "Noob Combo" or as the "EMP combo" where a rifleman will use a Plasma Pistol to down the shields of an opponent and then fire a single headshot to kill the opponent, killing an enemy with only two shots. The BR55HB SR's accuracy and range also make it an option to suppress enemy snipers, as continual bursts disrupt the aiming of these enemy sharpshooters.

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 really a three-round-burst, certain movements can break up the grouping and greatly reduce accuracy. 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).

However, the BR55HB SR is not as effective at close ranges. Each bullet acts as a tracer which gives away the shooter's position, and the range is limited at long distance in comparison to the SRS-99D-S2 AM. It also does negligible damage against vehicles, though can still cause Warthogs and Mongoose ATVs to spin out if the wheels are shot.

Physical Description and Appearance
The BR55HB SR is a bullpup, selective fire (Except in Gameplay), UNSC rifle that fires the 9.5x40mm X-HP-SAP round (see below). It fires from a 36 round magazine which fits flush in the receiver. The receiver is built directly into the underside of the butt of the rifle and is located behind the grip.

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 (although not illustrated in-game) can either be pulled back and locked, or, it can be fully cycled after a fresh magizine 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 rifle 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 BR55HB SR, having a rifled barrel, 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.

Changes From The BR55

 * Modified optical rail
 * New Trijicon ACOG-style scope
 * New trigger guard
 * Longer barrel
 * New reloading animation
 * Less magnetism
 * Slightly different firing sound
 * Slightly lower rate of fire

Besides these aesthetic changes, the BR55HB SR is functionally identical to the BR55.

Ammunition
It is interesting to note the ammunition used for the Battle Rifle. It uses a new 9.5mm x 40mm Experimental Round. The 7.62 x 51 mm NATO round is a rather high-powered round used in the MA5B-C Series and on many modern-day assault rifles, designated marksman rifles (DMR), and machine guns. The 7.62 mm has a history of having too much recoil because of the round's high power, which made it hard to fire in full-automatic. While the BR55's larger 9.5 mm round would be heavier and would thus presumably generate even more recoil than the 7.62 mm NATO, this is not necessarily the case. Since the Battle Rifle's rounds have a noticeably shorter case length than the 7.62 mm NATO (40 mm vs. 51 mm), they most likely contain much less powder than the 7.62 mm NATO, which would yield less muzzle energy and thus less recoil, making the weapon more manageable. However, the 40mm case may just be downsized to save space and house a more efficent powder, which in turn would yield more power for the volume burnt, and the increased bullet diameter may have been a comprimise to allow for a harder but less dense bullet material to achieve better penetration against armor; yielding the same or even more power.

Influences
The BR55HB SR Battle Rifle's design is strongly based on its predecessor, the BR55 Battle Rifle. However, it appears to have been aesthetically inspired by the French FAMAS.

Character Compatibility
This is the compatibility of the Battle Rifle in Halo 3.
 * Elites
 * Spartans
 * Marines
 * Brutes
 * Flood Combat Form (Human)
 * Flood Combat Form (Elite)
 * Flood Combat Form (Brute)

Trivia

 * Technically, "HB" could stand for "Heavy Barrel" which indicates the lengthened barrel of this variant. "SR" could stand for "Scoped Rifle", which is simply an additional description of this model.
 * In the Halo: Arms Race trailers and in Halo Wars, the BR55HB SR Battle Rifle seems to be automatic. But in Halo 3, however, it only fires in bursts of three rounds. This is most likely due to inaccuracies in the film, an automatic firing mode not used in the games due to balance, or a restricted feature only occasionally used in BR55 Battle rifles.
 * This weapon fires very similarly to the Heckler & Koch G36 and the Colt AR-15 which fires using the Short-Stroke Gas-Operated Rotating-Bolt, aside from the fact that most trigger assemblies for the G36 use a two shot burst.
 * 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.
 * WETA Studios made a replica Battle Rifle, Magnum, Sniper Rifle, Carbine, Gravity Hammer, Brute Grenade, Rocket Launcher, and Plasma Pistol to use in the currently-on-hold Halo film.
 * In mutiplayer, some players consider the Battle Rifle a necessity due to it's range and compatibility.

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 * BR55 Battle Rifle