M16A4
Fourth variant of the M16 family: flat-top upper receiver with Picatinny rail for modular optics.
M16A4
Community
Data trust
- Reliability
- Partially verified
- Sources
- Field Medical Service Technician Student Handbook (M16/M4 family, June 2013)US Marine Corps · Accessed
- Last reviewed
Identity
- Designation
- M16A4
- Manufacturer
- Colt / FN Herstal
- Country
- United States
- Year
- 1997
- Category
- Assault rifle
- Status
- In service
Ballistics
- Caliber
- 5.56×45 mm NATO
- Muzzle velocity
- 948 m/s
- Rate of fire
- ~800 rpm
- Effective range
- 550 m
- Maximum range
- 3600 m
Dimensions
- Barrel length
- 508 mm
- Overall length
- 1000 mm
- Empty weight
- 3.9 kg
Mechanics
- Operating system
- Direct gas impingement
- Bolt / action
- Rotating bolt
Feed
- System
- STANAG magazine
- Standard capacity
- 30 rounds
Fire modes
Production & service
- ●M16A1 — First service variant adopted in 1967 in Vietnam.
- ●M16A2 — 1983: 3-round burst, redesigned sights, stiffer barrel.
- ●M16A4 — Picatinny RIS handguard and removable carry handle.
Historical profile
Development
The M16A4 emerged in the late 1990s as an upgrade of the M16A2 (1982) based on USMC requirements. The key change was the flat-top upper receiver with a MIL-STD-1913 Picatinny rail in place of the integrated carry handle, allowing quick mounting of modular optics (ACOG, RCO).
It was Type Classified Standard in 1998 and became the standard USMC infantry rifle from 2003, progressively replacing the A2.
Design
The rifle retains the M16A2's 508 mm barrel and Eugene Stoner's direct gas impingement system (AR-15, 1959): gases are channeled directly into the bolt group through a tube, a lightweight solution but sensitive to carbon fouling.
The selector provides safe / semi-auto / three-round burst (FN burst cam). The KAC RAS handguard adds side and bottom rails for accessories; the stock is a fixed polymer A2 type.
Operational service
The M16A4 was the iconic US Marine rifle in Iraq (Fallujah 2004) and Afghanistan, where its long barrel delivers the full velocity of the M855 round at medium and long range. It also remains in service with allied armed forces (Philippines, Iraq).
From 2015 the Marine Corps moved to the M4 and then to the M27 IAR as the standard squad weapon: the M16A4 has been progressively relegated to support units and marksman roles.
Key components
- ●Stock — Fixed stock on the M16A4 service-rifle configuration, distinct from the M4 carbine’s telescoping stock.
- ●Receiver — Flat-top upper receiver with Picatinny rail and removable carrying handle; the rifle uses the Stoner direct-impingement gas system.
- ●Grip — Separate pistol grip on the M16A4 service-rifle lower receiver.
- ●Magazine — Detachable STANAG-pattern box magazine for 5.56×45 mm NATO ammunition, typically holding 30 rounds.
- ●Barrel — 5.56×45 mm NATO rifle barrel; the M16A4 configuration pairs it with an accessory-rail handguard.
Compatible optics (4)
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