Interdynamic MP-9
A rare Swedish-designed submachine gun with limited U.S. production.
The Interdynamic MP-9 is a fully automatic, 9mm submachine gun that operates via blowback. The U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) classifies it as such. Its construction relies on inexpensive molded polymer and stamped steel. Magazine capacities include 10, 20, 32, 36, and 50 rounds.
The design originated with Interdynamic AB in Stockholm, Sweden, which aimed to produce a low-cost submachine gun for military use. Failing to attract government interest, the company never manufactured the gun in Sweden. Instead, Interdynamic created a U.S. subsidiary to market a semiautomatic version to civilians, called the KG-9 (named after partners George Kellgren and Carlos Garcia). The ATF forced Interdynamic USA to redesign the KG-9 because it was too easily converted to full-auto. The required changes included a closed bolt and a retooled lower plastic receiver with a metal serial number tag on the side, replacing the original stamped serial number in the plastic magazine well. This revised model was designated the KG-99.
The MP-9 submachine gun itself was an open-bolt, fully automatic version of the KG-99. The upper and lower receivers of the KG-99 and MP-9 are identical, except the MP-9 has a bolt hold-open slot milled into the upper receiver and a compensation slot cut into the muzzle tip. Interdynamic produced very few registered MP-9 submachine guns due to low public demand. Two configurations exist: a select-fire model with a collapsible stock (the Interdynamic MP-9), and a stockless, fully-automatic-only variant (the K-9). Total production is believed to be under 50 units, with perhaps as few as 24 of the select-fire, collapsible-stock version.
Illegally made copies of a similar 9mm machine pistol, marked "Intratec TEC-9," have been seized in Europe.
Quick Facts
- Is Ranged
- yes
- Origin
- Sweden
- Production Date
- 1983–1984
- Part Length
- 173 mm (6.8 inches)
- Cartridge
- 9×19mm Parabellum
- Feed
- 10, 20, 32, 36 and 50-round magazines
- Action
- Straight blowback, open bolt
- Rate
- 1000 rounds/min
- Velocity
- 366–427 m/s (1200–1400 ft/s)
- Weight
- 1.7 kg (3.9 pounds)
- Length
- 328 mm stock closed, 541 mm stock extended (13.25" stock closed, 21.3" stock extended)
- Range
- 55 m
Facts from the source article.
Lore & Background
The MP-9 originated from a design by Interdynamic AB of Stockholm, Sweden, intended as a cheap submachine gun for military applications. Unable to secure government interest, the company never entered production in Sweden. Instead, Interdynamic set up a U.S. subsidiary to market a semiautomatic version, the KG-9, to civilians. The ATF forced a redesign of the KG-9 due to its ease of conversion to full auto, resulting in the KG-99. The MP-9 was the open-bolt submachine gun configuration of this redesigned platform.
The MP-9 and KG-99 share identical upper and lower receivers, except that the MP-9 has a bolt hold open slot milled in the upper receiver and a compensation slot cut into the muzzle tip. Interdynamic produced a very small quantity of registered MP-9 submachine guns due to lack of public demand. Two configurations were made: a select-fire version with a collapsible stock (Interdynamic MP-9) and a fully automatic only version with no stock (K-9). Production numbers are believed to be less than 50 total, perhaps as few as 24 select-fire guns with the collapsible stock.
Illegally made copies of a similar 9 mm machine pistol, marked "Intratec TEC-9", have been seized in Europe.
Reader's Guide
The Interdynamic MP-9 represents a footnote in submachine gun history, notable more for its design lineage and scarcity than for any widespread use. Its development illustrates the challenges of marketing a military-oriented design to civilian markets, particularly under ATF scrutiny. The MP-9's direct relationship to the semiautomatic KG-99 and the earlier KG-9 highlights the regulatory pressures that shaped its final form. The extremely low production numbers—fewer than 50 total, with possibly as few as 24 select-fire examples—make it a rare collector's item. The existence of illegally made European copies marked as Intratec TEC-9 indicates that the design's simplicity and low cost continued to attract interest outside legal channels. The MP-9's legacy is largely tied to the broader Intratec TEC-9 family, which saw more commercial success. Its story underscores how a design originally conceived for military contracts can evolve through regulatory and market forces into a niche civilian product, and how even a failed military project can leave a trace in the form of a few registered submachine guns.
Did You Know?
- The MP-9 is made of inexpensive molded polymer and stamped steel parts.
- The MP-9 and KG-99 share identical upper and lower receivers except for a bolt hold open slot and muzzle compensation slot.
More in Submachine Guns, Part 3 1-16
Spotted an error? Know more?
Reader corrections go straight into our review queue. Suggest an edit · How this site is sourced