Interdynamic MP-9 SMG: Origin of the TEC-9

Published on August 13, 2025
Duration: 11:50

This guide details the field stripping and reassembly process for the Interdynamic MP-9 SMG, a precursor to the TEC-9. It emphasizes the firearm's simple design, featuring a single cross pin for disassembly and a robust bolt assembly. The process is presented with a focus on mechanical understanding, suitable for intermediate users.

Quick Summary

The Interdynamic MP-9 SMG, a precursor to the TEC-9, was designed in Sweden and later adapted for the US civilian market. It features a simple open-bolt blowback action, a polymer frame, and a collapsing wire stock. Its design's simplicity led to legal challenges, necessitating a redesign to the closed-bolt KG-99.

Chapters

  1. 00:00Introduction and Origins
  2. 00:55Move to the US and Commercialization
  3. 02:17External Features and Markings
  4. 03:45Stock and Sights
  5. 05:12Disassembly and Internal Components
  6. 07:27Trigger Mechanism
  7. 08:47Legal Impact and Company Evolution

Frequently Asked Questions

What was the Interdynamic MP-9 SMG?

The Interdynamic MP-9 SMG was a simple, open-bolt submachine gun designed in Sweden by George Kellgren. It served as the direct precursor to the TEC-9 pistol after Kellgren moved to the US and adapted the design for the civilian market.

How did the MP-9 lead to the TEC-9?

Designer George Kellgren brought the MP-9 design to the US, forming Interdynamic USA. They converted the open-bolt MP-9 into a semi-automatic pistol called the KG-9 for civilian sales. This evolved into the Intratec TEC-9 after legal challenges and company changes.

What are the key design features of the Interdynamic MP-9?

The MP-9 features a polymer frame with an embedded metal serial number plate, a collapsing wire stock, and operates on an open-bolt blowback system. It is chambered in 9mm Luger and uses magazines derived from the Swedish K SMG.

Why was the KG-9 redesigned into the KG-99?

In 1982, the ATF ruled the open-bolt KG-9 a machine gun. This legal decision forced a redesign to the closed-bolt KG-99 to comply with federal regulations and maintain its status as a semi-automatic firearm for civilian sale.

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