M6I

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The M6I is a selective fire machine pistol and is one of the 's variants.

Design details
A selective fire pistol, the M6I possesses a selector switch allows the user to either fire semi-automatically or fully-automatically. The weapon typically uses magazines that hold ten rounds, but optional twenty-round magazines are also available. The M6I is also compatible with the six-round magazines used by the. Like the rest of the M6 series, the M6I is short recoil operated, using the recoil left by the previous shot to load the next round into the chamber. The barrel of the M6I is threaded, allowing the attaching of a. The M6I can also be fitted with various other attachments, such as tactical lights,, and detachable stocks.

Ammunition
Unlike many of the other pistols of the M6 series, the M6I is chambered for a smaller, less-powerful 10.9×33mm cartridge, as opposed to the cartridge. The 10.9×33mm is noticeably weaker than the 12.7×40mm, but possesses significantly less recoil, allowing the M6I to be more controllable in automatic fire. Regardless, as a magnum-caliber round, the 10.9×33mm is quite powerful itself.

SAP HE
M6Is used by the  are most commonly loaded with  (SAP HE) rounds. Each of these rounds possesses a hardened steel jacket and is filled with a stable explosive. The hard jacket enables the round to penetrate body armor and enter the target, but is structured to deform shortly after entering in order to prevent the round from exiting the body and causing accidental casualties on the other side of the target. The explosive is then ignited by a fuse, detonating the entire projectile inside the target's body, producing a devastating wound that is crippling if not outright lethal.

HEC
Another, less common military cartridge variant is high-explosive concussion (HEC). Unlike the SAP HE round, the HEC only possesses a copper jacket with more explosive filling, which is detonated by an incendiary material at the tip that is first ignited by the round's impact. Instead of penetrating the surface and then exploding inside the target, an HEC round creates a larger explosion at the target's surface, creating a shockwave that stuns and disorients the target, should he/she/it survive the shot. Combined with the high rate of fire of the M6I, HEC rounds are capable of pinning down heavier infantry such as and. Inevitably, HEC rounds are less lethal than SAP HE rounds and are only effective in specific applications, warranting its limited use in the UNSC Defense Force. An HEC round is labeled with a painted red tip.

7.87×37mm SLAP
The 7.87×37mm SLAP is based on the 10.9×33mm necked down to accept a 7.87mm sabot encasing a 5mm Staballoy penetrator. The sabot allows for a smaller, lighter projectile in a relatively large cartridge, resulting in a significantly higher velocity and sectional density when fired. The dense, high-velocity projectile offers very effective armor penetration capabilities, exceeding those of the and even the. Also due to its high muzzle velocity, the 7.87×37mm SLAP possesses a much flatter trajectory when fired, resulting in a greater effective range and better accuracy compared to those of more-standard rounds. As the cartridge possesses the same overall dimensions as those of the 10.9×33mm, the only adjustment to an M6I that would need to be made in order to accept the 7.87×37mm would be a simple barrel swap.

Civilian cartridge variants
10.9×33mm can also come in the form of full metal jacket, jacketed hollow-point, and soft-point, all of which are available to  and civilians.

Variants
The M6I is available in a few additional configurations, each with a distinct model name.

M6I/US (US—"up-sized")


 * The M6I/US is a larger, up-sized variant of the M6I, possessing a longer grip, allowing it fit in the hands of a wearing .  The weapon performs exactly the same as the standard variant does otherwise.  Due to the extended grip, the M6I/US cannot accept the M6K's 6-round magazines.

M6I/B (B—"burst")
 * Unlike the standard M6I and the M6I/US, the M6I/B has a five-shot burst mode in place of the fully-automatic function.

M6I/B/US (B/US—"burst/up-sized")
 * The M6I/B/US is the up-sized variant of the M6I/B. Like the M6I/US is to the standard M6I, the only difference an M6I/B/US has from an M6I/B is a longer grip that enables the former to be wielded by a SPARTAN wearing MJOLNIR armor.  Also like the M6I/US, the M6I/B/US cannot accept the M6K's 6-round magazines because of its longer grip.

Trivia

 * There are several notable users of the M6I.
 * Dom-094 often uses a customized M6I/B/US as his sidearm. Throughout most of his career, is customized M6I/B/US was rebarreled for 7.87×37mm rounds, and was attached with a, a smart-linked red dot sight, and a tactical light.  However, starting October 2558, Dom-094 replaced his M6I/B/US's 7.87mm barrel with a 10.44mm barrel, loading it instead with HEC rounds, and fitting it with a new set of attachments consisting of a  and a  scope.
 * Fred-G068's sidearm of choice is a customized M6I/US fitted with with a and a tactical light.  Fred-G068 carries a detachable stock separately, and may or may not attach it to his M6I/US, depending on the situation.
 * Alex Oxley uses an M6I/US rebarreled for 7.87×37mm rounds as his sidearm. His M6I/US is fitted with a  sight and a detachable stock.
 * Lloyd Harris uses an M6I/US as his sidearm, sometimes attaching it with a stock.
 * From the last year of the onward, Reginald Harding carried a pair of M6I/USs to complement his affinity for sniper rifles.  Equipped with extended 20-round magazines, the machine pistols served as lethal and incredibly fast close-range weapons.
 * I consider the  analogous to the present-day .45 ACP, the former of which is a large, standard-issue handgun cartridge, and the latter of which is a relatively large handgun cartridge that is standard-issue in many modern militaries.  I decided to make up a handgun cartridge for the UNSC that would be analogous to the smaller, present-day  9×19mm Parabellum.  I settled on basing the dimensions of the cartridge off those of the real-world .44 Magnum, as the 12.7×40mm’s dimensions are very similar to those the real-world .500 S&W Magnum.  The main difference between the M6I's 10.9×33mm and the .44 Magnum is that high explosive ammunition does not come in the form of handgun rounds in the modern real world.  Another difference between the M6I's 10.9×33mm and the .44 Magnum is that the former is rimless while the latter is rimmed.
 * The properties of the 7.87×37mm cartridge is based on those of the 6.5×25mm CBJ Ball cartridge, which can pierce armor more effectively than the 7.62×51mm NATO (likely M80 FMJ) can.