5.56x45mm NATO cartridge

The 5.56x45mm NATO cartridge is a NATO-standard small-arms cartridge in FN Herstal's SS109 lineage, and Colt identifies the AR15A4 Rifle as chambered in 5.56x45mm. This relationship-only page captures the cartridge's technical context and direct rifle match without inheriting conflict-use claims from the rifle page.

5.56x45mm NATO cartridge, 5.56x45mm NATO small-arms cartridge, Munitions

Image source: 5.56 x 45 mm NATO.jpg

Profile

Origin: Belgium
Built by: FN Herstalmultiple licensed ammunition manufacturers
Built in: Belgiummultiple countries
Type: 5.56x45mm NATO small-arms cartridge
Service note: Late 1950s development; NATO-standardized in 1980
Designer: FN Herstal for the SS109 cartridge lineage adopted as NATO standard
Designed: 1950s; NATO SS109 standard adopted in 1980
Unit cost: Varies by load, manufacturer, and contract
Produced: 1950s to present
Number built: Produced in very large quantities by many manufacturers
Variants: SS109 / M855 ball, Tracer, Blank

cartridge NATO portable small arms

Specifications

Cartridge family: 5.56x45mm NATO / 5.56 NATO
Standardized load lineage: SS109, designed by FN Herstal and adopted by NATO as the second official standardized calibre in 1980
Representative service loads: Ball, tracer, and blank variants are listed by FN Herstal
Compatible platforms: Carbines, assault rifles, and light support weapons in 5.56x45mm NATO chamberings
Case type: Small-arms bottleneck cartridge

Service And Conflict Use

Service History

In service: Standard small-arms ammunition for compatible NATO chamberings and commercial equivalents
Used by: NATO-aligned rifles, carbines, and light support weapons

Rifles That Fire It

Colt identifies the AR15A4 rifle as chambered in 5.56x45mm, which is enough to document a direct compatibility link for this cartridge page.

Firing weapon	Weapon type	Source-backed relationship
AR-15-pattern rifle	5.56 mm self-loading rifle platform	Colt explicitly describes the AR15A4 rifle as chambered in 5.56x45mm.

Firing Weapons

The cartridge page links back to a cataloged rifle platform that Colt identifies as chambered in 5.56x45mm.

Firing weapon

Weapon type

Firing evidence

AR-15-pattern rifle

5.56 mm self-loading rifle platform

Colt explicitly identifies the AR15A4 rifle as chambered in 5.56x45mm, making it a documented firing weapon for this cartridge.

Sources: AR15A4 Rifle

5.56x45mm NATO cartridge Images

5.56x45mm NATO cartridge, 5.56x45mm NATO small-arms cartridge, Munitions - view 1 — Source: 5.56 x 45 mm NATO.jpg

5.56x45mm NATO cartridge, 5.56x45mm NATO small-arms cartridge, Munitions - view 2 — Source: Rifle cartridge comparison w scale.png

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Sources

AR15A4 RiflePublisher: Colt's Manufacturing Company | Note: Supports the Colt AR15A4 rifle's 5.56x45mm chambering and representative rifle-cartridge compatibility context. | Accessed: 2026-06-23 5.56x45MM NATOPublisher: FN Herstal | Note: Supports the 5.56x45mm NATO designation, SS109 lineage, NATO standardization, representative ammunition types, and compatible platform classes. | Accessed: 2026-06-23 5.56 x 45 mm NATO.jpgPublisher: Wikimedia Commons | Note: Supports image provenance for a representative 5.56x45mm NATO cartridge photograph. | Accessed: 2026-06-23 Rifle cartridge comparison w scale.pngPublisher: Wikimedia Commons | Note: Supports image provenance for a cartridge comparison image that includes 5.56 NATO. | Accessed: 2026-06-23