M62 light machine gun

The M62 light machine gun was a magazine-fed, air-cooled, gas-operated, selective fire infantry weapon used by the United Nations Space Command during the Human-Covenant War. The M62 was designed to give soldiers operating within a squad additional range and volume of fire without drastically increasing weight. The M62 utilised the 7.62x51mm NATO round, a well-balanced round in comparison to alternative calibres, its accuracy and rate of fire, combined with negligible recoil, making it well suited for use in the M62. The gun provided infantry squads with the heavy volume of fire of a machine gun combined with accuracy and portability approaching that of a rifle.
==History==
A contract for a fully automatic squad support weapon was issued shortly after the beginning of the Human-Covenant War by the UNSC, to fill the gap between its infantry's assault rifles and heavy machine guns, thus providing a boost to firepower, mobility and flexibility within the UNSC's infantry units. Misriah Armouries won the contract with their prototype XM62 Light Machine Gun, which was put into full scale production in late 2532. The M62 was a popular weapon as it was powerful, relatively lightweight and reasonably compact, as well as having better than average accuracy and superb resistance to abuse. Within a number of years, at least one infantryman within a squad was armed with the M62, enabling them to support their squadmates with sustained automatic fire of the sort previously only provided by cumbersome and immensely heavy machine guns.
==Usage==
The M62 Light Machine Gun was designed to give infantry squads a lightweight weapon capable of laying down sustained automatic fire, to a greater degree than assault rifles. In addition to augmenting a squad's firepower, it was capable of providing suppressive fire against targets, affecting the accuracy of their return fire and in so doing supporting squadmates. The M62 was issued at squad level at one per squad; the light machine gunner would then fill a support and direct fire role within the squad, increasing its effectiveness in combat. The M62 was useful at nearly all ranges; at close range its high rate of fire making up for its large size. At longer ranges the weapon was fairly effective provided the operator utilised it correct way; for example, avoiding fully automatic fire and firing from a prone position or with a bipod increased the probability of a hit considerably. The weapon's most effective range, however, was between fifty and four hundred metres, where its large magazines and fully automatic modes made it a serious threat and its relatively unwieldy nature was not an issue. The M62 was an effective weapon in most combat environments, though as a rule fared better in battlefields where close quarters contact with the enemy was rare.
==Design==
The most striking aspect of the M62's design was its bullpup layout, which positioned the action and the magazine behind the trigger. This layout increased barrel length compared to the overall weapon length, which had the effect of increasing muzzle velocity and therefore range. The weapon was most commonly fed by an M14 drum magazine, a detachable helical magazine with a capacity of two hundred 7.62x51mm NATO caseless rounds. However, the weapon could be operated using the M9, a 42-round detachable box magazine used by the MA6 assault rifle. Box magazine feeding was used only as an auxiliary measure, when drum ammunition had been exhausted. The M62's removable rail interface system consisted of a total of four attachment rails; one along the weapon's upper receiver, one along the forward handgrip and two on the weapon's sides. The weapon was equipped with day and night iron sights which could be adjusted for windage and elevation; these sights were not removable but could be folded down when not in use. Side-mounted rails would commonly be used for laser aiming modules, rangefinders or flashlights, or a range of more advanced aids for the operator including, for example, folding LCD displays which could be linked to the user's HUD and electronic sight. The bottom rail was most regularly used for attachment of a vertical foregrip to help control muzzle climb in automatic fire, and a bipod or tripod which was essential for accurate, sustained stationary fire. The rail though could accommodate underbarrel weapons such as the M11 Tactical Shotgun, though these were rarely mounted due to the already significant weight and size of the weapon. The fire mode selector was located directly above the enlarged thumbhole stock and trigger assembly; between this and the magazine well was the magazine release, which was located on both sides of the weapon. The weapon's external furniture and grip were constructed from lightweight fibre-reinforced polymer, made of a polymer matrix reinforced with fibres (a carbon fibre/kevlar mix). The material allowed for a lightweight though immensely strong construction. The rails and magazine assembly were constructed from high grade steel, while the receiver and firing mechanism were precision-machined titanium alloy. The weapon featured no quick barrel replacement mechanism, meaning the weapon needed to be stripped to replace the barrel. However, the fluted barrel was constructed from a titanium/ceramic metal matrix composite lined with a super heat and friction resistant silicon carbide ceramic matrix composite. This gave the barrel an effective life of 30,000 rounds before it needed replacing, as well as reducing its weight over steel barrels by 56%, and largely eliminating overheating weapons even after sustained fire. The weapon was modular, meaning that it was assembled in interchangeable sections that were easy to separate and replace, in addition to its rails which accepted a wide range of attachments. 
The M62 was a relatively light weapon for its size as a result of its weight saving materials, however still weighed much more than assault rifles; this, coupled with its larger calibre and fully automatic role, meant that recoil control was imperative. Several hydraulic buffers linked to the weapon's microprocessor accurately controlled recoil, effectively attempting to cancel it out it and reducing it considerably. The weapon also 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. This caused the bolt to 'bounce' 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 long and heavy barrel and forward grip combated any muzzle climb. The barrel end featured a large flash suppressor which reduced the barrel's muzzle flash and directed it away from the shooter's vision; as a secondary function this vented excess gas in a way counteractive to the weapon's muzzle climb and backwards recoil.
The M62's cocking handle was located along the upper receiver, and was accessible through both sides of the weapon. As the M62 utilised caseless ammunition, it lacked an ejection port or any mechanism of extracting and ejecting a casing.
==Ammunition==
The M62 used 7.62x51mm NATO ammunition, which was a commonly used round in assault rifles and light machine guns. Lighter than most UNSC calibres, it was nonetheless perfectly suited to light machine guns such as the M62; the round offered controllable recoil together with good range, accuracy and adequate stopping power. The round achieved less range and power than other infantry cartridges, notably the 9.5x60mm battle rifle round, due to its smaller size and decreased kinetic energy; however, this allowed for higher rates of fire and more controllable weapons, balancing its capabilities out and affording it good suitability for automatic weapons.
The weapon, like nearly all UNSC weapons, utilised caseless ammunition, which had several advantages over traditional cased ammunition. This was a major change from Great War-era weapons, which utilised rounds which contained propellant inside metal casings. From the conclusion of the Human-Covenant War onwards, the UNSC worked on increasing the lethality of its infantry firearms; aside from the development of directed energy weapons, one element the UNSC looked at was the application of caseless ammunition. This was already used with operational success in the M7/Caseless Submachine Gun, though was limited to this weapon and not available in other calibres. Developments in technology, however, allowed the widespread adoption of caseless ammunition from around two decades after the war onwards, with newer replacement weapons discarding more traditional ammunition.
Unlike experimental caseless munitions of the late 20th century, the M62's ammunition maintained a tolerance similar to traditional, cased bullets. This was achieved by the propellant being coated in a thin layer of water, heat and dirt resistant coating. This also allowed rounds to be handled and manually loaded, as well as improving their 'drop resistance' or shock tolerance significantly. This also increased its shelf life considerably. These qualities were present in the M7/C Submachine Gun's ammunition, and carried over to the UNSC's next generation of caseless weapons.
Caseless ammunition offered several advantages. The most noticeable was an increase in muzzle velocity; not only was more propellant available per bullet with the caseless system, the propellant released significantly more energy when combusted. This higher muzzle velocity led the M62 to deal noticeably increased damage to the target in terms of kinetic effects; this also markedly improved its armour and shield penetration characteristics. The 7.62mm round's muzzle velocity was typically two to three times higher with caseless ammunition than traditional cased types, making it significantly more effective than its more traditional predecessors and meaning even assault rifles were capable of taking on shielded and armoured Covenant infantry. It was largely this increase in lethality that convinced the UNSC to maintain ballistic weapons for the bulk of their weapons, rather than developing and adopting plasma weapons of their own.
Caseless ammunition also reduced the complexity of the M62's internal mechanisms, as there was no need for extraction and ejection of spent casings. As the overall round was smaller, it allowed for larger capacity magazines, and its significantly reduced weight increased the amount of ammunition a soldier could realistically carry.
The 7.62mm bullet was actually embedded inside the solid propellant 'block'; it, the bullet and the primer were held together by a combustible glue. When fired, everything in the chamber save the bullet fully combusted, leaving no residue in the chamber and propelling the bullet down the barrel. The propellant itself was an advanced solid, plasma-based substance similar in composition to that of the the experimental M634 HP-SAP, which gave high muzzle velocity; this in turn increased lethality on contact with the target. The block was highly resistant to temperature, which prevented it from combusting prematurely or 'cooking off', for example on contact with heat inside the weapon or external heat sources.
There were numerous forms of 7.62x51mm NATO ammunition available to the UNSC, each differing in usage and effects. This varied from the simple and cheap to the complex and expensive to manufacture. The most commonly issued and utilised round was the M602 S/AP-HE, or Shield/Armour Piercing-High Explosive, which was a balance of potency and cost. Specialised ammunition, such as the M601 SAP-HEI, was generally only issued to high priority units and special forces, while forms such as the M603 Jacket Hollow Point specialised to a degree where they were limited in their effectiveness, and as a result were not commonly issued.
*M601 Semi-Armour Piercing-High Explosive Incendiary: The M601 Semi-Armour Piercing-High Explosive Incendiary, or SAP-HEI, was an ammunition type combining both an armour piercing and an explosive/incendiary capability. The bullet's tip was filled with a highly incendiary chemical, which burned at several thousand degrees upon impact with a target, damaging or melting armour and heavily affecting shields. Behind this was a high explosive component which detonated immediately on impact with a target, further damaging the area. Behind this was a solid core penetrator of depleted uranium, held in a backing 'cup' of steel. The components were held together in a copper or lead jacket. Upon hitting a target, the incendiary and explosive properties would damage the target area, aiding considerably in the depleted uranium's penetration into the interior. The penetrator featured a self-sharpening tip and was itself pyrophoric, meaning that it ignited upon impact with the incendiary material. It then punched through any remaining armour, having been ignited at this point and also carrying with it any remaining incendiary material from the tip. Effects on the target, especially if it was organically-based, were catastrophically damaging; the round would typically bypass any present armour (following rapid depletion of shields) and propel an incendiary penetrator and secondary incendiary material into the target's innards. However, the round's complexity in design made it expensive and its use was usually reserved for special forces and select few line units.
*M602 Shield/Armour Piercing-High Explosive: The M602 Shield/Armour Piercing-High Explosive, also known as S/AP-HE, was the most common and effective type of ammunition employed in the 7.62x51mm calibre. The bullet itself was coated in a polymer which acquired an electric charge while in flight, aiding the bullet's kinetic energy in depleting shielding and, although it had little effect on armour, increased the bullet's drain on shielding by roughly half. The further the bullet travelled in the air, the greater the charge it acquired, so this effect was at its most potent at longer ranges and nearly negligible at extreme close range. The tip of the round consisted of a deforming ballistic cap; a lightweight element which crumpled upon impact with a target and gave the bullet superior aerodynamic characteristics. The bullet's armour-piercing core was a 'CVT' (Chromium Vanadium Tungsten) and Austenitic Steel alloy with a self-sharpening tip; when it fractured upon impact, it would do so in a way that the remaining element was still a sharp point. Behind this was a pre-fragmented block of 'TC3' alloy, composed of tungsten, cerium and copper carbide, with a delayed action fuze in the centre. This alloy maintained similar incendiary and pyrophoric properties to uranium, though without associated radiological effects. A millisecond after the bullet's penetration of the target, the fuze would activate; this fuze contained a plasma-based high explosive compound, which explosively fragmented the pre-weakened TC3, in turn heavily damaging organic structures and internal organs. As a secondary function the TC3 was incendiary, causing severe secondary damage to soft targets.
*M603 Jacketed Hollow Point: M603 Jacketed Hollow Point (JHP) round was a specialised munition for unarmoured and lightly armoured infantry, being at its most effective when utilised against Kig-Yar and Unggoy.
*M604 Tracer: The M604 Tracer
*M605 Armour Piercing High Explosive: The M605 Armour Piercing High Explosive round (AP-HE) was an effective armour defeating round, used as a cheaper alternative to more expensive semi-armour piercing high explosive incendiary (SAPHEI) ammunition. The bullet's tip was composed of a hollow, lightweight ballistic cap which deformed on impact, and improved the bullet's ballistic properties. Behind this was an armour piercing penetrator composed of CVT (Chromium Vanadium Tungsten) and Austenitic steel alloy, with a self sharpening tip. The remaining length of the bullet was comprised of 'stressed' steel; the interior of this steel was hollowed out and contained explosive filler and a delayed action fuze. Shortly after impact this would detonate, fragmenting the steel and causing effects similar to a miniature fragmentation grenade, albeit designed to detonate inside an organic body.
*M606 High Explosive Squash Head: The M606 High Explosive Squash Head round, or HESH, was designed to deal damage to a target without needing to defeat its armour, thus making it ideal for shielded and armoured targets. The bullet was formed of a thin steel shell filled with plastic explosive, with a delayed action base fuze towards the rear. Upon impact with a target the bullet would deform and form a disc or 'pat' of explosive with an increased surface area. A millisecond later the base fuze detonated, creating a shock wave that, owing to its large surface area and direct contact with the target, was transmitted through the material. The round was able to effectively defeat active shields due to primary kinetic, secondary explosive and tertiary kinetic effects. If impacting on armour, the round would cause little damage to the armour itself but directly damage the target through the resulting shockwave. This shockwave was highly disruptive to internal organs, often tearing vital organs from their connective vessels or reducing them to a thick paste. In some cases, the shockwave would cause a secondary effect known as spalling, where minute fragments of the armour's internal layer would be projected off it at high velocity, known as spall. In these cases secondary damage was enhanced by a sort of fragmentation effect inside the target's own body, and caused by their own armour. The round was relatively cheap to produce and was effective against unarmoured, armoured, unshielded or shielded infantry targets.
==Gallery==
Category:UNSC Weapons