L403A1 Assault Rifle: Technical Specifications

L403A1 Assault Rifle: Technical Specifications


Heckler & Koch (Germany)

The L403A1 Assault Rifle, also known as the Alternative Individual Weapon (AIW) system, represents a significant leap in military firearm technology. This report provides a comprehensive overview of the rifle\’s specifications, historical background, and current deployment.



Gas-operated, selective-fire rifle


5.56x45mm NATO

Barrel Length:

16 inches (standard configuration)


7.3 pounds (unloaded)

Rate of Fire:

700-900 rounds per minute


Effective Firing Range:

Up to 600 meters

Feeding System:

30-round detachable box magazine

Muzzle Velocity:

Approximately 3,100 feet per second

Safety Features:

Ambidextrous safety lever, preventing accidental discharge

Rail System:

Picatinny rail system for mounting optics and other accessories


Collapsible and adjustable for length

Operating System:

Gas-piston, with a rotating bolt


Capability for under-barrel grenade launchers, bipods, and other accessories

Special Features:

  • Improved gas system for enhanced reliability
  • Chrome-lined barrel for extended service life
  • Modular design for easier maintenance and customization

This technical specification aims to provide detailed insight into the L403A1 assault rifle, a critical part of the British Royal Marines\’ new armament. Its features such as reliability, customizability, and overall design make it an ideal choice for the specialized operations conducted by these elite forces.

The L403A1, originally known as the KS-1, is a product of the Knight\’s Armament Company (KAC). It was selected by the British Armed Forces in 2023 to replace the L85A2-A3 and L119A1-A2 rifles. This selection was part of Project Hunter, aimed at equipping special operations forces with a modernized weapon system. The L403A1 was chosen over competitors like Heckler & Koch, SIG Sauer, and Glock, due to its advanced features and reliability.

Technical Specifications
The L403A1 boasts a highly efficient, self-indexing gas system, enhancing the rifle\’s durability and reliability. Its fully-ambidextrous lower receiver and enhanced bolt carrier group, featuring a proprietary bolt, make it a versatile weapon suitable for various combat situations. The rifle is chambered in 5.56x45mm NATO and is available in four barrel lengths. Its 13.7\” heavy-profile barrel, with distinctive ball-mill dimpling, aids in weight relief and cooling, maintaining performance even in intense combat scenarios.

Deployment and Usage
The British Army and Royal Marines are the primary operators of the L403A1. An initial order of 1,620 rifles was placed under a £90 million contract, with options to procure up to 10,000 systems over the next decade. The rifle system includes advanced optics and a signature reduction system, enhancing the effectiveness of troops in high-threat environments. Its compatibility with the rifle systems used by many of the UK\’s allies allows for efficient skill and drill sharing among special operations forces.

Manufacturing and Supply
The L403A1 is being manufactured and supplied by Edgar Brothers, a UK-based contractor. The rifle is a culmination of components from various reputable suppliers, including Knight’s Armament Company, Vortex Optics, Aimpoint, and Magpul. The system includes a rifle with a suppressor, low power variable optics, red dot sights, and training systems like Safe Blank Firing System and Marker Round Training System. This collaborative effort ensures the L403A1 is equipped with the latest technology and meets the rigorous standards of modern warfare.

The L403A1 Assault Rifle is a testament to modern engineering and strategic military needs. It offers a blend of advanced technology, reliability, and versatility, making it an essential asset in the arsenal of the British Armed Forces and potentially other militaries worldwide.

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