|This article, M392 Designated Marksman Rifle, was written by The All-knowing Sith'ari. Please do not edit this fiction without the writer's permission.|
The M392 Designated Marksman Rifle (more formally, Designated Marksman Rifle, Caliber 7.62 mm, M392) is a selective fire rifle chambered for the 7.62x51mm NATO cartridge in use by the United Nations Space Command Defence Force.
The M392 is made with the intention of carrying out both designated marksman and CQB roles in combat. As a result, it mounts Picatinny Combat Attachment Points on all four sides for the attachment of optics, aiming modules, and ancillary weapons. It saw widespread use throughout all branches of the UNSCDF until to 2548, when it was superseded in use by the larger-calibre BR55 rifle in all branches but the Army.
The UNSC Army commissioned ArmaLite to develop the DMR in 2392 to fill the niche between medium-ranged assault rifles and machine guns and long-ranged sniper rifles. In contrast to specialised sniper teams, designated marksmen provide an additional capability to their infantry squad by being able to engage targets at greater ranges than the other members of the squad by virtue of the DMR's longer barrel and improved optics. In contrast to sniper rifles, the M392 can be used in both long-range and close-quarter battle roles.
The M392 saw great use in all four branches of the UNSCDF throughout the Insurrection, but its future was thrown into question in the 2520s when the UNSC Marine Corps became concerned that the its 7.62mm cartridge would be unable to penetrate advanced Insurrectionist ballistic battle armour captured from UNSC depots, or donated by sympathisers within the CMA. As a result, they commissioned ArmaLite to develop the XBR55 prototype rifle, a long-barreled, scoped weapon firing the 9.5x40mm SAPFMJ cartridge, powerful enough to pierce ballistic vests. In range tests, the rifle proved able to penetrate an armoured target at a range of 1200 metres. When the Insurrection abruptly concluded with the Covenant's attack on Harvest, some questioned the need for the BR55, after units reported that the M392 performed satisfactorily against Covenant units. However, the Marines and Navy issued the BR55 anyway, and was well-received by users and it had replaced the M392 as the standard DMR in all service branches by 2548, with the exception of the Army, who stuck to the M392 due to its marginally longer range, similar ballistic performance against Covenant warriors, and cartridge interchangeability with the MA5 rifle. The M392 remains in Army use.
The M392 is an air-cooled, magazine-fed, gas-operated select-fire bullpup rifle that fires 7.62x51mm ammunition, the same calibre as the MA5 rifle, allowing marksmen and riflemen to share rounds if necessary, though the magazines are incompatible due to differing receiver designs. The M392 features a 560mm, match grade titanium barrel, allowing for superior range and accuracy over the MA5 assault rifle and marginally longer range over the later BR55 rifle.
The M392 fires a variety of 7.62x51mm ammunition types. The most-often-issued round is the M118 Armour-Piercing, Full Metal Jacket cartridge, which allows for superior armour penetration, but without the risk of overpenetration and injuring civilians. The bullet is jacketed with copper-coated titanium and tipped and cored with tungsten. Upon striking body armour, the jacket penetrates before deforming, and will temporarily help maintain the shape of the projectile so that it has a better chance of penetration. A second impact against bone or solid muscle mass inside the target's body will complete the jacket's rupture, at which point the projectile mushrooms and fragments into smaller pieces, causing a large number of wound channels and maximising damage. The tail-heavy bullet also yaws and tumbles upon impact, creating a massive cavity. Another round is the M129 Semi-Armour-Piercing, High Explosive cartridge, issued when it is likely that soldiers will face a heavily-armoured enemy. Similar to the M225 SAP-HE rounds fired by the M6D PDWS, the round combines both an armour-piercing capability and a high explosive effect. The initial impact ignites a small quantity of incendiary material in the tip, triggering the detonation of the HE charge, thus blasting a path through the armoured target for the penetrator. The remaining element of the round is the tungsten penetrator. This has a large amount of kinetic energy and will penetrate the now-unarmoured target through the path created by the explosive. A pre-cut cross on the tip of the penetrator makes the bullet expand inside the body, increasing its diameter to limit penetration and produce a larger diameter wound. The triggering of the explosive charge is dependent upon the resistance of the target. If the target offers little resistance then the lack of frictional heating will prevent the incendiary from igniting and the high explosive from detonating, preventing collateral damage. The third type of specialist ammunition issued is the M130 Jacketed Hollow Cavity cartridge, controversially nicknamed the "shredder". This is a variety of hollow point bullet where the hollow is unusually large, so that the bullet fragments into several projectiles on impact. This spreads the damage over a larger area. These rounds are surounded with a fluted copper jacket in order to provide optimal fragmentation, as opposed to a haphazard disintegration which would do less damage. Despite their high effectiveness against unarmoured targets, they lack penetrative power and armour-piercing capability. All these ammunition types are available in red, green, blue, or infrared tracers, which feature a delay element to prevent the filler from igniting until it is some distance away from the shooter, allowing him to be better concealed.
The M392 rifle is a bullpup weapon and is made of lightweight titanium alloy and its handguards, pistol grip, and buttstock of polymers - the rifle is a gas-operated weapon with a rotating-bolt and therefore must be cocked before the first shot can be fired. The charging handle used to chamber the round is situated on the left side of the rifle and does not reciprocate 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. The charging handle then locks back and must be sent forward by pressing the bolt release catch on the weapon's left-hand side after a fresh magazine is inserted to load the next round. The magazine itself is located at the butt of the rifle and the magazine release button is located above the magazine well behind the trigger. The magazine is a double-column box design. An articulated mechanism which allows the block and bolt to recoil off-axis into a recess behind the weapon's magazine well, together with the barrel being in line with the shooter's shoulder, but also in line with the shooter's hand as with many target pistols, reduce felt recoil and muzzle climb by eliminating the distance between the shooter's hand and the bore axis. The M392 features two ejection ports, and can be transformed into a dedicated left-handed rifle by simply swapping the bolt and ejection port cover. The rifle features two trigger guards: a more conventional guard, and a larger trigger guard, which doubles as a hand protector and helps prevent the user from dropping it.
The bore and chamber, as well as the gas piston and the interior of the gas cylinder, are chromium-plated. This plating dramatically increases the life of these parts by resisting corrosion and wear. Due to this, and the abundant use of titanium in the weapon's design, the weapon requires zero cleaning or lubrication, though the designer states that cleaning is required after 10,000 rounds. The M392 is electronically fired, thus preventing jamming issues caused by breaking firing pins, and has a trigger mechanism with a fire-control selector that enables semi-automatic fire and fully automatic fire (the fire selector lever is located at the right side of the receiver, just ahead of the magazine). A cross bolt type safety prevents accidental firing and is located above the trigger; the "safe" setting blocks the movement of the trigger. The rifle features a cold-hammer forged barrel with a 20,000 round service life. The cold hammer-forging process provides a stronger barrel for greater safety in case of an obstructed bore or for extended firing sessions. This includes "OTB" (Over-the-beach) capability; the M392 can be safely fired after being submerged in water and not completely drained. The barrel features a "bird cage" slotted flash suppressor, which also serves as a mounting base for attaching a blank-firing adaptor or a bayonet. The flash suppressor is also threaded, allowing it to accept suppressors.
The M392 mounts Picatinny Combat Attachment Points on all four sides, allowing it to mount underbarrel weapons, laser designators, flashlights, and a variety of sights and scopes, which can be linked to the user's HMD. The rifle is typically issued with the 3x M157 Non-Electric Combat Optical Gunsight (NECOG). Its superimposed reticle, available in a variety of patterns and colours, is illuminated by an external fibre optic light-gathering rail when available light is plentiful, and by an internal tritium lamp during low-light use. It mounts secondary iron sights. Two hooks at the front and back of the weapon allow for the attachment of either the standard-issue three-point sling, or a CW sling that serves not just as a carrying strap, but also as an aid to greater hit probability by helping the shooter aim steadily.