GD-112

Type 112 machine pistol (GD-112)
GD-112 in its major configurations.
Type	Submachine gun
Place of origin	Menghe
Service history
In service	2012-present
Used by	Menghe Idacua
Wars	Innominadan Crisis Innominadan Uprising
Production history
Designer	Insŏng New Arsenal
Designed	2000s
Produced	2011-present
Specifications (GD-112G)
Weight	2.74 kg with full magazine
Length	stock extended: 604mm stock folded: 708mm (stock extended) 510mm (stock folded)
Barrel length	248mm
Cartridge	7.5×25mm 7.62×25mm 9×18mm 5.8×21mm FN 5.7×28mm
Rate of fire	900 rpm
Muzzle velocity	550 m/s
Effective firing range	200m
Feed system	10, 20, or 30-round magazine
Sights	Iron sights

The GD-112 (Formal designation: 112식 기관 단총 / 一一二式機關短銃, iriri-sik gigwan danchong, "Type 112 machine pistol;" Short designation 112식, iriri-sik, "Type 112") is a modular submachine gun developed in Menghe. Unlike most other submachine guns, it is gas-operated and fires from a closed bolt with rotation-based locking. These features result in greater safety, accuracy, and reliability. The weapon is primarily used by Menghean special forces, including the Deep Mission Troops, the IIA, and the Internal Security Forces. In Menghean service it is most often chambered in 7.5×25mm +P+ ammunition, but variants exist in a variety of other pistol calibers.

Development

During the 1990s and 2000s, Menghean servicemen and special forces personnel expressed complaints about the country's two existing submachine gun designs, the GD-71 and GD-98. Both were simple, rugged open bolt firearms, designed for maximum simplicity and ease of maintenance. Yet the tradeoffs involved in an open bolt weapon also caused problems, such as the lost accuracy resulting from the forward movement of the bolt immediately after a trigger pull.

The GD-71 in particular was plagued by misfire issues related to its rudimentary safety features, which were judged insufficient to prevent accidental dischages when dropped or handled roughly. The GD-98 addressed some of these, installing a ratcheting lever to prevent the bolt from being knocked back without the use of the charging handle, but it came with its own range of problems: the shorter barrel and lighter cartridge hampered accuracy, and the poor ergonomics of the L-shaped metal buttstock met heavy criticism from special forces.

Initially the Menghean Army held off on developing a new submachine gun, as the financial demands of expanding the Army to meet the threat from Maverica after 2005 outweighed concerns about special forces and police units. In 2008, after securing separate funds, Insŏng New Arsenal began an independent project to develop a more effective submachine gun in the hopes that it would later be adopted. The designers made extensive use of feedback from military personnel, including veterans of the Ummayan Civil War and training staff from Army academies, developing their own set of requirements in the process. The final product was presented to Army procurement staff in 2012 for assessment, and it passed all trials as a clear improvement over the GD-98, earning it approval for service under the designation GD-112.

Design details

Action

The GD-112 is relatively unique among submachine guns for its use of a closed bolt, gas-operated action. The layout of the internals is influenced by the JS-103 assault rifle and its TS-106 special forces carbine variant, both Hwasŏng designs, though the GD-112 uses a short-stroke gas piston. A rotating bolt keeps the chamber closed until after pressure in the barrel has fallen to safe levels, and the firing pin is floating inside the bolt, striking the cartridge when hit by a hammer connected to the trigger group.

Because the bolt is already forward and locked in place when the trigger is pulled, the GD-112 is capable of producing more accurate semi-automatic fire than its open-bolt counterparts. The use of a non-fixed firing pin provides additional safety, especially when combined with a retaining pin in the bolt to prevent the firing pin from coming forward when the selector lever is set to safe.

An additional advantage of the closed bolt design is that the breech is sealed and the ejection port covered when the bolt is forward, preventing sand and mud from entering the action. For additional protection, a spring-loaded panel can be folded up over the ejection port; this is automatically kicked open when the bolt is pushed back, either on firing or because the charging handle was pulled.

The charging handle itself is located on the left side of the foregrip, rather than the right side of the receiver. This allows the operator to cock the weapon using his left hand, immediately after inserting a magazine, without removing his right hand from the pistol grip or rotating the weapon. The charging handle is non-reciprocating, and works by pushing a metal rod into the bolt face to force it back; it is not physically attached to the bolt, and a spring holds it forward.

On Menghean-service weapons, there are three fire-selector options available: ㅈ (automatic), ㄷ (single-shot), and ㅇ (safe). On some custom-made variants, a burst mode is added, and the automatic mode may be removed to comply with civilian firearms regulations.

Ammunition

The service variant of the GD-112 used by the Menghean Deep Mission Troops and counter-terrorism units is chambered in an overpressure loading of the Menghean 7.5×25mm pistol cartridge. This loading achieves 34% higher pressure in the barrel than standard 7.5×25mm cartridges. The increased muzzle velocity results in greater range, accuracy, and armor penetration, all qualities valued by special counterterrorism units, though it also requires a sturdier and heavier weapon.

In part to avoid incompatible loading of ammunition types across firearms - which would result in poor performance on the GD-112 and dangerous parts failures on the GD-71]] - +P+ loadings of 7.5×25mm ammunition are issued in special magazines not compatible with earlier Menghean submachine guns. Standard service magazines for the GD-112 are built with polymer sides and an aluminum backplate, and use a release notch on the rear of the magazine, similar in layout to earlier Menghean magazines but dimensionally different.

To aid in reloading under adverse conditions, the GD-112's magazine well is "flared" outward by 8 mm forward and backward and 4 mm to each side, guiding a magazine inserted slightly off-angle into the right position. There is also a last-round bolt-hold-open system which alerts the user that the magazine is empty.

Construction

Unlike many other Menghean military weapons, which use stamped components where possible, the GD-112 has its upper and lower receiver halves cut from milled blanks. Though this results in added weight, it also increases the weapon's durability; cracking and bending were common on the GD-71 and GD-98, which used unusually thin metal in an effort to save weight. The barrel is attached to the upper half of the receiver, for a more stable connection with optics mounted on the top rail.

The outer wall of the upper receiver extends 7.5 centimeters ahead of the receiver's front plate. In addition to providing additional room for a longer rail on top, and thus more optics mounting options, this encloses the connecting rod and retaining spring of the charging handle.

Disassembly and maintenance of the weapon is relatively straightforward. The upper and lower receiver halves are linked by two captive pins, which can be pushed through by a disassembly tool or a spare cartridge. Once the handguard is removed by unlocking it and sliding it forward, the two halves of the receiver can be pulled apart. Two additional pins can separate the trigger group from the lower section.

Modularity

Because it was designed for special forces, police, and export customers, rather than Army conscripts, the GD-112 allows for a relatively high degree of customization. A MARS rail on top of the receiver and MASS slots in the handguard allow the attachment of optics, laser sights, flashlights, and foregrips, all compatible with Galenic and Dayashinese products. The handguard itself is slides into place along rails on the upper receiver, and can be traded out for a custom-built model with different rail and slot options.

In addition, many other components of the weapon can be removed and replaced as needed. The buttstock and pistol grip can be changed out to suit the user's preferred ergonomics or training. Notably, the barrel and gas tube can also be easily changed out in a depot; on top of the standard 248mm barrel for the regular service model, there are options for a 148mm "pistol length" barrel, a 440mm "carbine length" barrel, and a barrel/foregrip assembly with an integral suppressor.

Changing out the barrel and bolt also allow the weapon to be easily rechambered in another caliber, either during production or after purchase. Caliber options range from 5.45×18mm to .45 Super; magazine capacity varies in proportion to cartridge size.

Variants

Because the GD-112 uses a modular barrel which can be easily changed out in a depot, workshop, or owner's home, both the barrel length and the caliber can be customized as needed without permanently altering the weapon. Insŏng has marketed the weapon internationally under the following variant labels, but within the Menghean special forces it is common to group them all together as modifications of the GD-112.

• GD-112G: Technical designation for the basic variant of the firearm with medium-length barrel.
• GD-112SG: A silenced variant using a barrel with an integral suppressor.
• GD-112JG: A "carbine-length" variant with a long barrel and extended handguard.
• GD-112DG: A "pistol-length" variant with a 148mm barrel.

• BD-112: A custom-built version with semi-automatic capability only. Intended for police forces or the civilian market.

Users

• Idacua
• Menghe