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SNT Motiv STSM21

Modular Submachine Gun (SMG) [ 2024 ]

The modular-minded, tactical-level STSM21 submachine gun is currently under development by South Korea-based SNT Motiv.

Authored By: Staff Writer | Last Edited: 09/13/2022 | Content ©www.MilitaryFactory.com | The following text is exclusive to this site.

Currently (2022) under development by South Korean small arms-maker SNT Motiv is the "STSM21", a 9mm-chambered Close Quarters Battle (CQB) Warfighter solution. The design takes into account all proven modern trends in military-level automatic firearms design and presents it in a compact form suitable for urban fighting and SPECial OPerationS (SPECOPS) service. Modularity is at the forefront of this submachine gun with a long length of Picatinny rail set over the receiver - optional front and rear iron sights can be used while optics, aimers, and tactical flashlights. Construction is of durable metals as well as lightweight composites.

The design of this firearm is largely conventional: there is a small, lightweight, adjustable, and collapsible shoulder stock at the rear of the frame. The frame itself is home to the fire selector (within easy reach of the thumb), ergonomically-shaped pistol grip, and oversized trigger ring for a gloved hand. The magazine well sits ahead of the action in the usual way with the ejection port seen just above. All controls are ambidextrous to broaden the gun's market appeal and this includes the charging handle as well as the magazine catch. Magazines are of the straight type and house 20- or 30- 9x19mm Parabellum pistol cartridges. Internally, the gun makes use of the proven delayed blowback system-of-operation. The forend is perforated and the barrel is slotted.

One of the more unique features of the STSM21 is its use of a free-floating barrel, a practice common to sniper rifles where accuracy is the call of the day. The free-floating arrangement has the barrel only touching the frame along its length (and not the forend housing itself) to promote accurate fire.

Overall length of the gun reaches 680mm (600mm collapsed) with a 220mm long barrel assembly - making it ideal for close-quarters work due to inherent portability. Overall unloaded weight is 3.0 kilograms.©MilitaryFactory.com
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Service Year

South Korea national flag graphic
South Korea


Modular Submachine Gun (SMG)

National flag of South Korea South Korea (possible)
(OPERATORS list includes past, present, and future operators when applicable)
Special Forces
Qualities of this weapon have shown its value to Special Forces elements requiring a versatile, reliable solution for the rigors of special assignments.

Overall Length
680 mm
26.77 in
Barrel Length
220 mm
8.66 in
Empty Wgt
6.61 lb
3.00 kg

Optional Iron Front and Rear; Over-Receiver Optics Supported.


Delayed Blowback System.

Blowback Operation
Gas pressure from the rearward movement of the ignited cartridge case provides the needed bolt movement, ejecting the spent case and stripping a fresh case from the magazine.
(Material presented above is for historical and entertainment value and should not be construed as usable for hardware restoration, maintenance, or general operation - always consult official manufacturer sources for such information)


9x19mm Parabellum

Sample Visuals**

Graphical image of a 9mm pistol cartridge
Rounds / Feed

20- or 30-round detachable box magazine.
Cartridge relative size chart
*May not represent an exhuastive list; calibers are model-specific dependent, always consult official manufacturer sources.
**Graphics not to actual size; not all cartridges may be represented visually; graphics intended for general reference only.
STSM21 - Base Project Designation.

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Images Gallery

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Image from official SNT Motiv marketing materials.


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