Munitions

5.56x45 mm cartridge

Also known as
  • 5.56 NATO
  • 5.56x45mm NATO
  • 5.56 x 45 mm NATO
  • 5.56mm NATO
  • SS109
  • M855
  • M855A1

The 5.56x45 mm cartridge is the NATO-standard small-arms cartridge family derived from FN Herstal's SS109 work and standardized by NATO in 1980. The page tracks both the cartridge's technical lineage and direct conflict evidence, including Canadian 5.56 mm ammunition for Ukraine and U.S. Army M855A1 fielding in Afghanistan.

5.56x45 mm cartridge, 5.56x45 mm NATO small-arms cartridge, Munitions
Image source: Cartridge 5.56x45mm NATO CC BY-SA 4.0 by Grasyl.jpg

Role in Conflicts

Profile / Specs

Profile

Origin
Belgium / NATO
Type
5.56x45 mm NATO small-arms cartridge
Service note
Late Cold War to present NATO standard rifle ammunition
Designer
FN Herstal for the SS109 cartridge lineage adopted as the NATO standard
Designed
SS109 standardized by NATO in 1980
Produced
1980 to present for NATO-standard 5.56x45 mm service loads

Specifications

Caliber
5.56x45 mm NATO
Standard cartridge lineage
SS109 / M855 ball family
Representative U.S. improved load
M855A1 Enhanced Performance Round
Ammunition types
SS109 ball, L110 tracer, blank, and service-specific improved ball loads
Compatible weapon classes
Carbines, assault rifles, and light support weapons
NATO standardization
FN Herstal says SS109 was adopted by NATO as the second official standardized calibre in 1980
Service Load Structure

The cartridge family appears on this page as a service-ammunition family rather than a single factory load. FN Herstal documents the NATO SS109 baseline and associated tracer and blank loads, while U.S. Army sources document the M855 and M855A1 service-load path.

Load or designationDocumented roleSource-backed context
SS109 / M855Ball ammunition lineageFN identifies SS109 as the NATO-standardized cartridge; U.S. Army coverage ties M855 to M249 and M16A2 service.
M855A1Enhanced performance roundU.S. Army sources describe a 2010 Afghanistan fielding path and compatibility with the M4, M16, and M249 families.
L110 and blankTracer and training loadsFN lists tracer and blank options in its 5.56x45 mm NATO ammunition range.
Variants

This entry treats 5.56x45 mm NATO as a cartridge family. FN Herstal identifies SS109 as the original NATO-standardized 5.56x45 mm military load, while the U.S. Army M855 and M855A1 rows reflect American service-load development.

VariantConfigurationDesignation notes
SS109 / M855 ballStandard ball load lineage

FN identifies SS109 as its NATO-standardized 5.56x45 mm cartridge; U.S. Army coverage describes M855 as the Army's 5.56 mm round adopted for longer-range performance with the M249 and M16A2.

Sources: FN Herstal 5.56x45mm NATO, Evolution of the M855A1 Enhanced Performance Round

M855A1 Enhanced Performance RoundU.S. Army improved ball round

The U.S. Army describes M855A1 as a 5.56 mm enhanced performance round tailored for the M4 and improving performance in the M16 and M249 weapon families.

Sources: Army begins shipping improved 5.56mm cartridge

L110 tracerTracer load

FN Herstal lists L110 as the tracer ammunition type in its 5.56x45 mm NATO range.

Sources: FN Herstal 5.56x45mm NATO

BlankTraining and simulation load

FN Herstal lists blank ammunition as part of its 5.56x45 mm NATO cartridge range.

Sources: FN Herstal 5.56x45mm NATO

Firing Weapons

Catalog links below are limited to weapons or weapon families with direct source support for a 5.56x45 mm, M855A1, or equivalent 5.56 mm NATO relationship.

Firing weaponWeapon typeFiring evidence
M4/M4A1 carbine, Carbine, Infantry WeaponsM4/M4A1 carbineCarbine

The U.S. Army says the M855A1 5.56 mm round is tailored for use in the M4 weapon system.

Sources: Army begins shipping improved 5.56mm cartridge

M16 rifle, Assault rifle, Infantry WeaponsM16 rifleRifle

The U.S. Army says the M855A1 improves performance in the M16 weapon family and traces M855 adoption to M16A2 compatibility.

Sources: Army begins shipping improved 5.56mm cartridge, Evolution of the M855A1 Enhanced Performance Round

FN Minimi light machine gun, 5.56x45mm NATO light machine gun, Infantry WeaponsFN Minimi light machine gunLight machine gun

FN Herstal lists the FN MINIMI 5.56 as a light support weapon use case for its 5.56x45 mm NATO ammunition.

Sources: FN Herstal 5.56x45mm NATO

Arsenal AR-M9 / AR-M9F, 5.56 x 45 mm Kalashnikov-pattern assault rifle, Infantry WeaponsArsenal AR-M9 / AR-M9FAssault rifle

Arsenal product pages identify the AR-M9 and AR-M9F rifle family in 5.56x45 mm and 7.62x39 mm configurations.

Sources: 5.56x45 mm and 7.62x39 mm AR-M9, 5.56x45 mm and 7.62x39 mm AR-M9F

Why the family link matters

The same cartridge page can support rifle, carbine, and light-support-weapon relationships, but conflict rows are only listed where direct sources document the cartridge or a named 5.56 mm service load in that conflict.

Sources: FN Herstal 5.56x45mm NATO, Army begins shipping improved 5.56mm cartridge

Timeline

5.56x45 mm cartridge Key Events

  1. U.S. Army adopts the M16 rifle

    U.S. Army historical coverage states that the Army adopted the 5.56 mm M16 rifle in 1967 with the earlier M193 cartridge.

    Sources: Evolution of the M855A1 Enhanced Performance Round

  2. NATO standardizes FN's SS109 lineage

    FN Herstal identifies the SS109 cartridge as its design and says NATO adopted it as the second official standardized calibre in 1980.

    Sources: FN Herstal 5.56x45mm NATO

  3. U.S. Army adopts M855

    U.S. Army coverage describes the 1982 adoption of M855 to replace M193 and improve longer-range performance with the M249 Squad Automatic Weapon.

    Sources: Evolution of the M855A1 Enhanced Performance Round

  4. M855A1 shipping announced for Afghanistan

    The U.S. Army announced that it had begun shipping the M855A1 5.56 mm cartridge to support warfighters in Afghanistan.

    Sources: Army begins shipping improved 5.56mm cartridge

  5. Canada announces 5.56 mm ammunition for Ukraine

    Canada stated that 1 million rounds of 5.56 mm ammunition were scheduled for delivery to Ukraine as part of a larger small-arms and ammunition aid package.

    Sources: Canada May 2023 Ukraine military aid

Media

5.56x45 mm cartridge Videos

5.56x45 mm cartridge Images

5.56x45 mm cartridge, 5.56x45 mm NATO small-arms cartridge, Munitions - view 1
Source: Caliber cartridge comparison - .223 Remington and 5.56x45mm NATO.jpg
5.56x45 mm cartridge, 5.56x45 mm NATO small-arms cartridge, Munitions - view 2
Source: Army begins shipping improved 5.56mm cartridge
Related Weapon Systems
5.56x45mm NATO cartridge, 5.56x45mm NATO small-arms cartridge, MunitionsMunitions5.56x45mm NATO cartridge5.56x45mm NATO small-arms cartridgeThe 5.56x45mm NATO cartridge is the NATO-standard small-arms cartridge family built around FN Herstal's SS109 lineage, standardized by NATO in 1980 and produced by many ammunition makers. This entry tracks both its technical family context and direct conflict evidence, including Canadian 5.56 mm ammunition supplied for Ukraine, U.S. Army M855A1 fielding in Afghanistan, and 5.56 x 45 mm ammunition recovered from Islamic State forces in Iraq.
FN Minimi light machine gun, 5.56x45mm NATO light machine gun, Infantry WeaponsInfantry WeaponsFN Minimi light machine gun5.56x45mm NATO light machine gunThe FN Minimi is a Belgian belt-fed light machine gun developed by Fabrique Nationale for squad automatic fire, with 5.56 mm NATO models widely fielded as national variants such as the U.S. M249, Canadian C9, and Australian F89. In the 2014 Yemen Civil War, Amnesty International reported Belgian Minimis deployed by The Giants Brigades, tying the weapon to UAE-backed coalition-aligned ground forces around the Hodeidah offensive.
M16 rifle, Assault rifle, Infantry WeaponsInfantry WeaponsM16 rifleAssault rifleThe M16 is a U.S.-origin 5.56x45mm assault-rifle family that evolved from 1955 Vietnam War service into the M16A1, M16A2 and M16A4 lineage. Current Army and FN references describe the M16A4 as a gas-operated, shoulder-fired, 20-inch-barrel rifle with rail and optics compatibility, while conflict-specific sources document continued use from Marawi and Afghanistan to Israeli wartime response teams, Iraqi partner-force training and Colombian FARC dissident seizures.
FN MAG general-purpose machine gun, 7.62x51mm NATO general-purpose machine gun, Infantry WeaponsInfantry WeaponsFN MAG general-purpose machine gun7.62x51mm NATO general-purpose machine gunThe FN MAG is FN Herstal's Belgian 7.62x51mm NATO belt-fed general-purpose machine gun family, fielded from infantry bipods, tripods, vehicles, aircraft, ships, and boats. The catalog record connects the MAG and its M240/L7A2/MAG 58 designations to directly sourced conflict evidence: surrendered Boko Haram-held stocks in Nigeria, coalition base-defense training during Operation Inherent Resolve, and Afghan special-operations weapons training during the War in Afghanistan.

Sources

FN Herstal 5.56x45mm NATOPublisher: FN Herstal | Note: Supports manufacturer background, the 5.56x45 mm SS109 designation, NATO standardization in 1980, listed ammunition types, and compatible weapon classes including FN MINIMI 5.56. | Accessed: 2026-06-29Canada May 2023 Ukraine military aidPublisher: National Defence / Canadian Armed Forces | Note: Directly supports the 2014 Russia-Ukraine War row by documenting Canada's scheduled delivery of 1 million rounds of 5.56 mm ammunition to Ukraine. | Accessed: 2026-06-29Army begins shipping improved 5.56mm cartridgePublisher: U.S. Army | Note: Directly supports the 2001 War in Afghanistan row by documenting M855A1 5.56 mm cartridge shipments for warfighters in Afghanistan; also supports M855A1 background, M4/M16/M249 compatibility context, and U.S. Army image provenance. | Accessed: 2026-06-29Evolution of the M855A1 Enhanced Performance RoundPublisher: U.S. Army | Note: Supports U.S. 5.56 mm service-load history, including M16 adoption, M855 adoption, M249/M16A2 compatibility, and M855A1 design context. | Accessed: 2026-06-29Bulgarian AR-M9 & AR-M9F rifles supplied by UAE to allied forcesPublisher: Armament Research Services | Note: Supports the AR-M9 / AR-M9F caliber identification and the linked rifle-family context used for the relationship section. | Accessed: 2026-06-295.56x45 mm and 7.62x39 mm AR-M9Publisher: Arsenal JSCo | Note: Supports manufacturer background for the AR-M9 rifle family and its 5.56x45 mm / 7.62x39 mm product category. | Accessed: 2026-06-295.56x45 mm and 7.62x39 mm AR-M9FPublisher: Arsenal JSCo | Note: Supports manufacturer background for the folding-stock AR-M9F variant and its 5.56x45 mm / 7.62x39 mm product category. | Accessed: 2026-06-29Cartridge 5.56x45mm NATO CC BY-SA 4.0 by Grasyl.jpgPublisher: Wikimedia Commons | Note: Image provenance for the primary 5.56x45 mm cartridge photograph. | Accessed: 2026-06-29Caliber cartridge comparison - .223 Remington and 5.56x45mm NATO.jpgPublisher: Wikimedia Commons | Note: Image provenance for a cartridge comparison image that includes 5.56x45 mm NATO. | Accessed: 2026-06-29