BR60

The BR60 was an infantry weapon used by the United Nations Space Command following the Human-Covenant War. The direct successor of the UNSC's previous battle rifle, the BR55HB, the BR60 was an enormous leap forward from the BR55, featuring a longer barrel, advanced weight reducing materials, frictionless barrel coating and a selective fire capability. As a Battle Rifle, the BR60 fired a full-sized rifle round with increased range, accuracy and kinetic energy characteristics compared to assault rifles, giving a distinct advantage when facing Covenant forces. The rifle was also modular, allowing for a wide array of attachments to be added.

History
During the Human-Covenant War, the BR55 and its successor, the BR55HB, saw far more effectiveness against Covenant armour and shielding than the MA5C Assault Rifle. Mainly this was down to its calibre; the BR55 used M634 X-HP-SAP 9.5x40mm ammunition, rather than the 7.62x51mm NATO rounds used by the MA5 family. This increased bullet size meant a higher impact energy on contact with the target, better accuracy and increased range, all of which improved over the 7.62mm round. The BR55 was at first issued to designated marksman within infantry squads, but later was issued far more widely, second only to the MA5C. Its selective fire modes, accuracy and increased range over the MA5 rifles, along with its ease of use, meant the BR55 would continue to serve in UNSC forces in various forms for decades to come.

In 2560, when the ageing BR55 came up for replacement, the UNSC issued a contract for a 9.5x40mm modular rifle that could engage targets at over a kilometre and harass them at 1500m. Several competing companies put forward design prototypes, including Misriah Arms and Aperture Science. Misriah opted for a fully modernised, heavily updated battle rifle named the XBR60 that made use of various design and technical improvements since its predecessor was designed. Beating its competitors in several tests, the UNSC accepted the BR60 into service with the Marines and Army as a designated marksman and service rifle.

Usage
Despite being a Battle Rifle, the BR60's main usage, especially earlier in its deployment, was as a designated marksman rifle within squad-based combat. A small number of soldiers in a squad would be equipped with it to add a long-range rifleman capability to augment its firepower. Later on it was employed much more as a standard service rifle, seeing extensive usage by standard infantrymen, Marines, ODSTs and Special Forces units. Its long range in comparison to many other service rifles made it an excellent choice in large engagements; this, coupled with its large calibre round and relatively light weight, made it popular and widely used.

Design
The BR60 was gas-operated with a rotating bolt, meaning it needed to be charged before the first round can be fired. The charging handle was used to chamber the first round, while the following rounds are chambered and fired and the casings ejected using the high pressure gas from the round fired. The handle was located on the left side of the weapon, positioned at the front of the slide during operation and slid back to enable reloading. The magazine was housed in a receiver mounted on the underside of the stock, while the release catch was located on the right side of the weapon. The weapon's ejection port was located n the right side of the weapon, though it was fully ambidextrous and could be changed in a short amount of time without tools. The barrel itself was longer than the original BR55HB, meaning the bullet traveled for longer in the barrel, gained more spin from the rifling and as a result was more accurate, in addition to a higher muzzle velocity.

The barrel end featured a three-way muzzle brake reducing recoil, and was threaded to accept a suppressor. The weapon possessed rails on either side of the handgrip, the weapon's underside and the top side of the carrying handle, enabling a large amount of attachments to be quickly added according to required usage or user preference. A magazine release was located on either side of the weapon's external polymer casing near the magazine well. The rear of the BR60's upper receiver, above the action and firing mechanism, accommodated a removable adjustable cheeckrest that assisted in accurate long range fire. The weapon's upper receiver mounted a fore and rear foldable, removable ironsights that featured as standard on the weapon; they were frequently removed upon the use of more advanced optics. The weapon's handguard, sides and stock were constructed from lightweight yet strong and resistant polymer, as was the ergonomically-designed pistol grip. The upper receiver/carrying handle, rails and magazine assembly were constructed from high grade steel, while the barrel and firing mechanism were precision-machined titanium alloy.

Lighter than BR55, the BR60 experienced lower recoil despite this, mainly as a result of several recoil-reducing methods. The weapon featured a venting system that recovered part of the gases generated by the round, and pushed it back in a space located behind the bolt during the cycle. The bolt 'bounced' on a sort of 'gas cushion' that acted as a buffer, dramatically reducing the weapon's recoil. It also featured energy absorption mechanisms in the buttstock, absorbing energy and reducing felt recoil. The weapon's bullpup nature meant that it was somewhat back-heavy; however, the recoil reduction mechanisms largely balanced this out, and its rather heavy barrel combated any muzzle climb.

The rifle was modular, meaning that it was assembled in interchangeable sections that were easy to separate, in addition to its rails which accepted a wide range of attachments. The upper receiver or carrying handle, on which were mounted the iron sights and an attachment rail, was itself mounted on a rail and could be removed according to user preference, for example to reduce the weapon's size. This was, however, not an often used option as the fire mode selector, which was located on the left side of the upper reciever, needed to be relocated to a position just above the trigger; this was not a quick task and required the use of specialised tools. It also removed the vastly useful tactical computer. The cheeckrest module could also be detached, which was often the case when the handle too had been removed. Attachments such as optics and sights could then be mounted onto this rail. Integrated into the upper receiver was a tactical computer which was heavily expanded from that of the BR55, no longer just showing tactical waypoints and ammunition reserves. It was able to link to the user's neural interface, allowing it to display, in conjunction with the user's Heads-Up Display, large amounts of information pertinent to the user's needs. Much of this comprised tactical information about the combatant's immediate battlefield surroundings, including but not limited to friendly and hostile positions, topographical and meteorological data and current commands, objectives and targets.

BR60 Heavy Barrel
The BR60 Heavy Barrel, or BR60HB, was identical to the standard variant apart from that it featured a 36 inch (910mm) barrel instead of the usual 872mm (34 inch). This increased its accuracy, range and muzzle velocity markedly, though made the weapon rather large and unwieldy in close quarters combat and other space-restricted tasks. The heavy barrel also helped steady the end of the rifle, reducing muzzle climb when firing on full auto and in rapid bursts. This increased the accuracy and overall effective range of the weapon.