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This article is about the SMG introduced in Halo 2. For the SMG introduced in Halo 5: Guardians, see M20 SMG.
The M7/Caseless Submachine Gun (M7/SMG) is a personal defense weapon developed and manufactured by Misriah Armory. It is commonly used by infantry, special forces, and vehicle crews of the UNSC Armed Forces. A suppressed version of the weapon, the M7S SMG, is often issued to special operations personnel.
Originally, the M7 SMG was issued solely to vehicle crews as an emergency weapon; however, the submachine gun became widely used during the Insurrection. The weapon became favored by paramilitary police units and UNSC Special Forces units for its efficiency in eliminating insurgents located in orbital habitats and cluttered urban environments. Due to this efficacy, the M7 was also popular with those same Insurrectionists. Although the UNSC began trialing a replacement for the weapon, the M7 SMG remains the current submachine gun model used by the UNSC following the Human-Covenant War.
The M7/Caseless Submachine Gun is an automatic submachine gun that fires from a 60-round magazine which is placed horizontally on the left side of the weapon. Due to the odd horizontal placement of the magazine on the weapon, it can be assumed that the magazine utilizes a circular ramp where the magazine meets the breech. This rotates the horizontally stacked rounds in the magazine 90 degrees until they align with the horizontal breech. An example of this can be seen in the present day Fabrique Nationale P90 SMG.
The SMG has a polymer pistol grip, folding fore-grip, iron sights, and collapsible buttstock, as well as a titanium body. The SMG must be cocked before it can fire the first round. The charging handle is located on the right side of the gun and does not move during operation. Once the first round is fired, the gases from previous rounds force the breech to rotate and chamber a new round. Once the magazine is empty, the handle although not illustrated in-game, can either be pulled back and locked or it can be fully cycled after a fresh magazine has been housed. If it is first pulled back and locked, then it must be pushed forward in order to chamber a new round. The magazine release button is located between the red dots on the receiver and needs to be pressed before it can be flicked off. There is no ejection port due to the nature of the rounds fired.
The SMG has a rifled barrel that is 15 cm (5.9 in.) long. This weapon can also be affixed with a M49 sound suppressor; in this configuration, the weapon is designated the M7S Caseless Submachine Gun. The weapon is 47.4 cm (18.66 in.) long with the stock retracted and has a maximum length of 62.7 cm (24.68 in.) when the stock is fully extended.
Unlike most UNSC weapons, the M7 uses caseless 5×23mm ammunition, meaning it does not have a metallic casing surrounding the powder and sealing the bullet, propellant, and primer together. Instead of using this casing, the round uses a combustible adhesive to seal these components together. Because the adhesive and propellant are both vaporized when fired, there is no need to eject spent casings. Though not featured in-game, contemporary caseless ammunition is highly susceptible to cook-off, the accidental firing of rounds due to built-up heat in the receiver.
This feature is very beneficial. In addition to increasing fire rate by removing the extraction and ejection phases of the weapon's cycle, it reduces friction inside the magazine, one of the main causes of malfunctions in weapons. This is also conducive to dual-wielding, since the user need not concern themselves with hot brass expelled from the weapon held in the left hand. The projectile itself is jacketed in metal, usually a copper alloy in standard military ammunition, to aid in penetration of the target. Caseless rounds are actually embedded into the block of propellant, reducing their length, allowing more ammunition to be stored in a smaller space.
Nicknamed the "bullet-hose", the SMG is one of the best close-quarters firearm due to its large 60-round magazine and hit-scan properties. Suited for close-range combat, the SMG is extremely deadly against unshielded targets and can down shielded targets within seconds if dual-wielded.
The SMG can also form part of the most effective dual-wield combos in the game. The SMG, when dual-wielded with a Type-25 plasma rifle, can be a deadly combination as the plasma rifle depletes the opponent's shields with ease and the SMG rapidly tears through their health. Similar deadly combination, often referred to as the "noob combo", is dual-wielding the SMG and Type-25 plasma pistol. The charged shot from the plasma pistol will deplete the shield of the opponent and a full burst of SMG fire will tear through the now-exposed flesh and armor.
As aforementioned above, the SMG received the nickname "the Bullet-Hose" due to its high rate of fire, low accuracy, and inability to be fully controlled when fired in full-auto. The SMG's primary limiting factor is its poor accuracy, which limits its use to close range. At close-quarters combat, the SMG is only outperformed by the M90 shotgun, the Type-1 energy sword, and the Type-2 gravity hammer. Like most other human weapons, the SMG performs relatively poorly against shields, though this weakness is negated by wielding it in conjunction with a plasma rifle or plasma pistol. As stated before, the gun has recoil which causes the barrel to climb after continuous fire and will climb faster if players dual-wield it. This forces the players to continually move their reticule down to keep the enemy in their sights but is not a big limiting factor. This, as well as the poor accuracy can be slightly countered, using a burst-fire technique, unleashing about five bullets each pull of the trigger. It also has the problem of an extremely long reload time when dual-wielded, making it easy to be killed while changing magazines. This problem however can be solved by volley firing the weapons, so while one is reloading the other is still firing. This tactic reduces the power of having two SMGs but gives the advantage of approximately 40+ seconds of non-stop firing.
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